I sorta touched this subject on irc today, but I'd like to expand it here on forums.
I believe Mega Gallade is bit too much for the UU metagame. I have used both Sword Dance Gallade (the Knock Off version and Shadow Sneak version) and BU Gallade (Alternating between Sub and Taunt) and it consistently does its job (ie: wreck shit).
The Sword Dance hits absurdly hard, that's a pretty well known fact at this point. OHKOes everything at +2 except 3~ Pokemon, etc. Knock Off is better for wallbreaking stuff, but Shadow Sneak has its merits, like helping Gallade not get revenge killed by Mega Kazam or Scarf Chandelure. I could keep talking about this set, but not feeling like repeating what has already been said multiple times already.
The Bulk Up set is currently my favorite set. The most common version is Sub / BU / Drain Punch / Knock Off, it's bulky enough to not get its sub broken by some relatively weak special attacks and protects it from status (0+ Atk Jirachi Body Slam vs. 252 HP / 0 Def Gallade: 70-83 (20.5 - 24.4%) -- guaranteed 5HKO - Fuck Jirachi). I've been trying Drain Punch / Psycho Cut / Bulk Up / Taunt with decent success on the ladder (Currently 26-1 on the ladder, with 1500+~ points thanks to it), this set fits my team better because it actually uses stuff like Hippowdown as setup fodder and stops crap from setting up (since some people refuse to switch out against Gallade). Both version work basically the same way: Use BU and become impossible to OHKO, then stick around forever thanks to Drain Punch.
It seriously is virtually impossible to OHKO:
- 252 Atk Choice Band Crobat Brave Bird vs. +1 252 HP / 0 Def Gallade: 320-378 (94.1 - 111.1%) -- 62.5% chance to OHKO
- 252 SpA Chandelure Shadow Ball vs. 252 HP / 0 SpD Gallade: 254-300 (74.7 - 88.2%) -- guaranteed 2HKO
- 252+ Atk Tough Claws Mega Aerodactyl Aerial Ace vs. +1 252 HP / 0 Def Gallade: 206-246 (60.5 - 72.3%) -- guaranteed 2HKO
- 252+ SpA Mega Alakazam Dazzling Gleam vs. 252 HP / 0 SpD Gallade: 214-252 (62.9 - 74.1%) -- guaranteed 2HKO
- 252 SpA Choice Specs Raikou Shadow Ball vs. 252 HP / 0 SpD Gallade: 214-252 (62.9 - 74.1%) -- guaranteed 2HKO
- 252 SpA Hydreigon Draco Meteor vs. 252 HP / 0 SpD Gallade: 184-217 (54.1 - 63.8%) -- guaranteed 2HKO
- 252 Atk Sheer Force Darmanitan Flare Blitz vs. +1 252 HP / 0 Def Gallade: 187-222 (55 - 65.2%) -- guaranteed 2HKO
Some common things that outspeed (Gotta remember that with 110 the number of scarf-less Pokemon that do that aren't that many), the first four probably being the "worst case scenario" for Gallade in the entire UU metagame. As you can see revenge killing it is pretty damn hard and Drain Punch healing it back does not help at all and with Sub / Taunt defensive Pokemon have problems wearing it down. This set might not be able to outright OHKO the entire metagame (it still hits pretty hard with no investment tho, don't sleep on that 165 base attack), but its ability to basically not die as long as you cover the handful of Pokemon that can actually touch it without getting Drain Punch'd, make it a huge threat to every single playstyle.
PS: Inner Focus is useless 99% of the times, but it means Scarf Rachi cannot hax it to death and that Lopunny can't wear it down with Fake Out.