Deoxys Attack the Aggron of DPS calculators
Almost all of the DPS calculators list Deoxys Attack as the top counter, if they only used DPS and didn't consider anything else. Do not be fooled, I'm pretty sure Deoxys Attack is unusable because it can be killed in around 3 resisted fast moves.
Answers
Igglybuff, Carvanha, Jigglypuff, and Whismur are the only 4 currently released Pokemon to have lower defense than Deoxys-A.
What this means is as a raid boss it will be an incredibly easy solo, especially given its tier as a raid boss. If you're crazy enough to use one in battle your best hope is to hit something with a single Dark Pulse before getting knocked out.
Actually, there's a school of thought that posits that if you're going to get KOd by the first Charged attack, you might as well just have enough HP/Def to get there. So Deoxys attack might be useful as the first pokemon in certain raids, especially ones where the boss has a 1 bar move. That first move takes a while to charge up, and Deoxys attack can do a lot of damage before getting KOd. As a tissue paper cannon (glass is way too strong to describe Deoxys attack) in the lead off spot, it might actually be a viable contributor, because of a few quirks in how the battle develops.
I'm in the mindset of the amount of time necessary for each of its charge moves to connect. Poison Jab has an EPU of 7 with a cooldown of 0.80s and Zen Headbutt has an EPU of 10 with a 1.10s cooldown. PJ requires 8 uses to break 50 energy and ZH requires 5. This means it needs to survive for 6.4s when using PJ and 5.5s with ZH. This doesn't factor energy gain from taking hits and is in a raid/gym context, mind you.
From there it depends on the move being used. After tapped Dark Pulse takes 1.4s to connect and has an additional 1.6s cooldown after for a total execution time of 3s. Psycho Boost - for some unknown reason - takes 3.5s to connect and has a half second cooldown for a total time of 4s. This gives the following time frames for each move cycle:
ZH/DP: 8.5s
ZH/PB: 9.5s
PJ/DP: 9.4s
PJ/PB: 10.4s
I admit I haven't done any sims against what would constitute an ideal matchup but frankly I don't see it lasting much longer than those timers. Even with its ridiculous attack stat I'd be more inclined to use something that can survive four times as long at the cost of a couple theoretical DPS points.
I deliberately didn't touch on Zap Cannon because dear god why are you using a single bar charge move with a 3s connect time on something this fragile?
