http://www.smogon.com/dp/pokemon/ledian
With all due respect to whoever wrote the current Ledian analysis, it seems slightly lacking. The set comments are all relatively short and the Other Options section is basically empty. I've done a rewrite; it's a first draft so there's probably a few mistakes.
[SET]
name: Encore + Baton Pass
move 1: Swords Dance / Agility
move 2: Baton Pass
move 3: Bug Buzz
move 4: Encore
item: Leftovers / Focus Sash
nature: Timid
evs: 248 HP / 8 SpD / 252 Spe
[SET COMMENTS]
<p>By itself, Ledian struggles to do any sort of damage, however with Baton Pass it can really help a team out by passing Attack or Speed boosts around to more powerful team mates. Seeing as Ledian will rarely force switches, Encore helps to find enough free turns to stat up and pass your boosts. With Ledian's decent speed, you can come in on Earthquakes, Energy Balls or any set-up move, and Encore them to force your opponent to switch. This gives Ledian a much needed opportunity to stat up and Baton Pass out. If you can keep Stealth Rock off the field, Focus Sash is a good item choice in UU play to ensure that you manage to stat up at least once before Baton Passing. Otherwise, Leftovers is the superior option. </p>
[SET]
name: Substitute + Baton Pass
move 1: Substitute
move 2: Baton Pass
move 3: Bug Buzz
move 4: Agility / Swords Dance
item: Liechi Berry / Petaya Berry / Salac Berry
nature: Timid
ability: Swarm
evs: 248 HP / 8 SpD / 252 Spe
[SET COMMENTS]
<p>A different take on Baton Passing. This set is slightly harder to pull off than the first set as it struggles to force switches. However, with Substitute, Ledian can Baton Pass its boosts to a frail Pokemon with considerably less risk. It also allows you to pass boosts in two stats, depending on the stat-up move and the berry you elect to use. With these EVs, you ensure that you can come into Stealth Rock twice without fainting, or alternatively use Substitute four times as opposed to three, giving Ledian more opportunities to set up. </p>
[SET]
name: Support
move 1: Knock Off
move 2: Bug Buzz
move 3: Light Screen / Reflect
move 4: Roost
item: Leftovers
nature: Calm
evs: 248 HP / 8SpD / 252 Spe
[SET COMMENTS]
<p>Ledian's only stand-out stat is Special Defense, and this set takes advantage of that. Ledian makes a decent switch into a small number of UU threats, most notably the many Grass types such as Venusaur, Vileplume and Meganium. With Ledian's good speed, you can typically put up a Light Screen before many slower special attackers can hit you, allowing you to sponge the damage from several hard hitters much more easily. Roost allows you to recover off any damage taken and come in repeatedly. This set does run into several problems though. With Stealth Rock slicing 50% off Ledian's health every time it comes in, its switch-in opportunities are numbered. Furthermore, Ledian's poor defensive typing means that most sweepers carry a move that will hit Ledian for 2x damage, meaning that Ledian struggles to come in on much bar the aforementioned Grass types and Choice attacks.</p>
[SET]
name: Swords Dance
move 1: Swords Dance
move 2: Aerial Ace
move 3: Brick Break
move 4: Double-Edge / Baton Pass
item: Life Orb
nature: Jolly
evs: 252 Atk / 4 SpD / 252 Spe
[SET COMMENTS]
<p>With 169 Attack, Ledian isn't going to be hurting much. However, with one Swords Dance and a Life Orb, you're still operating with around 440 Attack. The lack of a consistent bug attack is a real problem here, leaving Ledian with Aerial Ace as its most reliable physical STAB attack. Brick Break provides good coverage with Ledian's flying STAB and really helps Ledian to get through the Rock/Steel types who otherwise wall it horribly, such as Aggron, Probopass and the uncommon Bastiodon. For the last slot, Double-Edge is probably the best option as it is more powerful than anything else in Ledian's movepool, and with such a low Attack stat Ledian needs all the power it can get. However, when you come up against something that Ledian can't KO, which you will find happens very often, Baton Pass is useful to give the boosts to something that is harder for the opponent to wall. </p>
[SET]
name: Choice Specs
move 1: Bug Buzz
move 2: Hidden Power Flying
move 3: Focus Blast
move 4: U-Turn / Giga Drain
item: Choice Specs
ability: Swarm
nature: Timid
evs: 252 SpA / 4 SpD / 252 Spe
[SET COMMENTS]
<p>With a small number of useful resistances and a nice Special Defense stat, you should find a few opportunities to get in and hurt something with this. STAB Bug Buzz is an obvious choice and can hurt if you can get your HP down low enough to activate Swarm; a relatively easy feat to achieve with Stealth Rock everywhere. Hidden Power Flying provides secondary STAB, and Focus Blast provides excellent coverage. The last slot is largely filler; U-Turn is the recommended choice so that you can scout your opponent's switch to switch to an appropriate counter, while Giga Drain helps against Gastrodon and Quagsire. </p>
[Other Options]
<p>Ledian's movepool is small, and has few other noteworthy moves. Reflect can be very useful, as most opponents will typically target Ledian's much lower physical defense stat. However, even with a Reflect up, Ledian will struggle to take most physical hits due to such a low base stat and poor defensive typing. Toxic helps to make up for Ledian's lack of real offense and can help wear down tanks such as Blastoise and Meganium. Silver Wind's stat boosts could be useful on a Baton Pass set. Offensively, Ledian also gets Ice Punch and Thunderpunch, which can both fit on the Swords Dance set. Mach Punch is pretty cool, but with no STAB and such a weak Attack stat it will rarely KO even the most frail of opponents, unless backed by several Swords Dances. </p>
<p>Ledian has two very mediocre abilities; Swarm and Early Bird. Swarm may see some use on more offensive sets or the Substitute variant, but for the most part Ledian's choice of ability is largely insignificant.</p>
[EVs]
<p>Baton Passing and Support sets will generally want near-max speed and HP, with a Timid or Calm nature. If you do decide to drop your Speed EVs, make sure not to go below 216, or you risk losing out to Venusaur. On the more offensive sets, just max out the offensive stat you are using and speed. Put the remainder anywhere but HP, so you can come into Stealth Rock twice before fainting. </p>
[Opinion]
<p>Ledian has a large number of problems that make using it in competitive play rather unappealing. A 4x weakness to Stealth Rock, a very poor movepool and bad stats don't do it any favours. It can make a decent Baton Passer, but in both OU and UU there are better choices for the role, notably Scizor, Gliscor, Celebi, Leafeon and Scyther. When considering Ledian for a team in any tier, you will generally find that something else does whatever Ledian does better. </p>
[Counters]
<p>Ledian's lack of real offense makes countering Ledian a relatively easy affair. However, seeing as most Ledian will be Baton Passing stat boosts of some kind, stopping it can be slightly harder. In OU, should you ever face a Ledian there, Skarmory, Hippowdon, Swampert are all very effective choices, being able to Roar any Baton Passers out whilst taking little damage from Ledian's other attacks. They all commonly carry Stealth Rock too, which severely cuts Ledian's lifespan. Anything else that has the option of carrying Roar or Whirlwind will easily stop a Baton Passing Ledian, examples being Zapdos, Suicune and Snorlax. </p>
<p>Even in UU, Ledian is countered very easily. For Baton Passers, Drapion, Noctowl, Blastoise, Aggron, Nidoqueen, Steelix, Altaria and Walrein are just a few Pokemon who have the option of carrying a phazing move and who take little damage from most of Ledian's attacks. If it is not Baton Passing, then Probopass, Flareon, Muk, Ninetales and Mantine all beat it easily. For the most part, anything that isn't weak to Bug Buzz will be able to switch in on most variants without much trouble.</p>
