Icy Man, sorry, I just didn't want to make the post even longer than it was going to by adding a quote :) But before I go, I just want to thank you for making such good points about Deoxys-E, it really challenges me to think of appropriate counter-points. I'm sorry if it seems that I'm ragging on your posts, but this is my first time responding to something like this, trust me, I did not meant it to be ragging.
On the contrary, I really do appreciate the feedback. This is also my first big discussion topic, so I'm kind of figuring things out too.
Thinking in math class, I came up with similar ideas of possible counters for Deoxys E - normals, and powerful pursuiters.
I'm not that great at damage calcs, I generally set them up wrong, but how much would TechBoost Lo Scizor and CB Stab Tyranitar Pursuit's do?
Depends on the EV spread, but I'll just go with max / max Bold for worst-case scenario.
-Adamant 252 Atk LO Tech Scizor using Pursuit on 252 / 252 Bold Deoxys-L (no switch): 394 Atk vs 460 Def & 304 HP (60 Base Power): 98 - 116 (32.24% - 38.16%)
-Adamant 252 Atk LO Tech Scizor using Pursuit on 252 / 252 Bold Deoxys-L (on a switch): 394 Atk vs 460 Def & 304 HP (80 Base Power): 128 - 152 (42.11% - 50.00%)
A hefty portion indeed from Scizor. I'm not sure if Technician still boosts the power of Pursuit on the switch, so someone who does know this would have to check it.
-Adamant 252 Atk CB Tyranitar using Pursuit on 252 / 252 Bold Deoxys-L (no switch): 604 Atk vs 460 Def & 304 HP (40 Base Power): 116 - 138 (38.16% - 45.39%)
-Adamant 252 Atk CB Tyranitar using Pursuit on 252 / 252 Bold Deoxys-L (switch): 604 Atk vs 460 Def & 304 HP (80 Base Power): 228 - 270 (75.00% - 88.82%)
Losing 75% minimum on the switch is nasty, especially since it will be coming back into Sand and a likely Stealth Rock (18% total).
In terms of Normals, these are the ones in OU, there are none in BL.
Blissey
Togekiss
Snorlax
Porygon-Z
For the first three, though they may force Deoxy's-E out, I think that Taunt will cause them to be easily set up upon. Deoxy's E may even outstall a Blissey if it Taunts correctly, because, Blissey will run out of the attack move it carries. Togekiss might be a bit harder, but I doubt it would pack the punch without being able to Nasty Plot immediately. Snorlax also poses a threat having a nice base attack. Unfortunately, Snorlaxes really rely on curses. So Togekiss would probably be the best of those three.
I completely forgot about Togekiss. However, defensive Togekiss has Thunder Wave (so it outspeeds and flinchhaxes you unless you also have Thunder Wave), and it runs Roost as well, so it boils down to who has more PP / Toxic. Nasty Plot Togekiss will also outspeed, so it flinches you until Taunt wears off, NP as you Taunt again, then rinse and repeat. Finally, the encore supporter runs near max speed and Timid - so it encores you once Taunt wears off (which it will thanks to flinchhax).
The last one however I think poses the best threat to Deoxys-E. Especially, when using Download, Porygon-Z packs the power and sheer number of attacking moves to beat down Deoxys-E.
Download is a bit of a risky option for P-Z, so if it doesn't get the sp.atk boost it may not win without Dark Pulse. Adaptability Scarf P-Z, though, can still pack a punch with Tri Attack, so P-Z is another option.
You are right, though, it would be interesting to test this pokemon to see what people really view as the most dangerous set. I don't think it would make it to OU, but, I'd be curious.
This brings me to Toxic Spikes. After thinking about it for a long hard time I came up with a good lead for a Deoxys-E team. It is this...
Infernape w/Focus Sash
-Fake Out
-Flamethrower
-Thunderpunch
-Earthquake
It has no other use than for a Deoxy's E team, and hits ALL POKEMON THAT USE TOXIC SPIKES SUPEREFFECTIVELY. It might have trouble with Cloyester and Omnastar though.
Basically, it acts like a regular lead, tries to kill things and die, unless the opponent is using a t-spiker. In which case, it fakes out, and then uses the appropriate move.
Sadly though, Tentacruel (the most common user of Toxic Spikes) will probably be able set up TSpikes as you come in, survive at least 1 Thunderpunch, Surf you away, and then MAYBE get down that second layer. Infernape is not really an option for "countering" pokemon (which is what this set attempts to do), especially the more defensive ones. Secondly, using Infernape like this really isn't the best way to use its sweeping potential.
After you have finished off the T-Spiker, you bring Deoxys in. There are several uses to doing so. First, off, they cannot bring in another T-Spiker without dying to Infernape. Second, I found that Deoxys-E has another use - forcing people to reveal their primary sweeper early. In other words, you bring in Deoxys, Taunt, if you're lucky, switch with knowledge of their sweeper if you are not. And becaus they won't be able to setup (Taunt), it is much safer than other pokemon.
Deoxys-E I think would be set up early, in this manner.
Oops, I forgot to mention recovery, Taunt prevents non Leftovers Recovery.