+1 4 SpA Pixilate Sylveon Hyper Voice vs. 252 HP / 0 SpD Deoxys-D: 136-162 (44.7 - 53.2%) -- 31.3% chance to 2HKO
+2 252 SpA Espeon Stored Power (260 BP) vs. 252 HP / 0 SpD Deoxys-D: 281-331 (92.4 - 108.8%) -- 56.3% chance to OHKO
I don't know if that is 'somewhat well', Espeon with 12 boosts (+4 Def&Speed with 2 CM's, probably not the hardest to get) and Sylveon at +1 pose pretty good threats to Deo-D. Scolipede doesn't need any boosts to outspeed, and if it passes +1 speed to Espeon on taunt then you've got a decent trouble on your hands, since it can begin setting up CM. Also, +1 smeargle outspeeds so it can spore you if they pass on a predicted Seismic Toss.
Seismic Toss however does allow it to take on BP subs, since most of them are less than 100HP. So I guess I can see it as a troublesome pokemon for BP to face, but probably not all that hard to work around if it comes in a bit too late.
Is phys defensive deo-d standard? I always figured with that nasty knock off and pursuit weakness deo-d would run specially defensive and just leave the phys tanking for someone else.
Regardless, I still say that the prediction war of deo-d vs BP is still heavily in deo-d's favor, for the following reasons.
1. You only need to land taunt once to stop the chain. One bad mispredict on the opponent's side means a broken chain.
2. An espeon with few to no boosts cannot stay in on deo-d, taunted or otherwise. Espeon is cleanly 4hko'd by s-toss, and does jack squat with stored power (seriously, if you let them boost for 6-ish turns to hit +6 speed and +6 defense without landing a taunt, you dun goofed, simple as that). If espeon tries to setup, it WILL take hits, and it cannot boost enough to threaten out deo-d before deo-d kills it. Given that morning sun espeon is rare-ish(4-MSS is BPs worst enemy), that damage is likely going to stay, making it all the harder for the opponent to swap in espeon on a predicted taunt.
3. Sylveon can be troublesome, but if sylveon uses hyper voice, you can taunt it, because a sylveon using hyper voice is a sylveon not swapping to espeon. Once taunted, just swap in your team's sylveon counter and force it out (every team should have something that can swap into +1 sylv and threaten it out)
4. Sleep powder and spore are the reasons why every team should have sleep fodder on it. Yes, smeargle forces deo-d to switch (unless you are running magic coat, which is not unheard of, but lets ignore that for a minute), but if you swapped in say, mega-venu, he forces a switch too (due to risk of leech seed or sleep powder). Also, if smeargle comes in on a predicted s-toss, that means sash is broken and is unlikely to come back via healing (more relevant to offensive teams then defensive, but relevant nonetheless).
So yes, I consider deo-d to be able to take on BP "somewhat well". He's not 6-0ing the BP team unless you run a moveset dedicated to beating BP (and even then it's not guaranteed), but with a relatively small amount of team support (sleep fodder + sylveon swap in, which happens to be two roles that have a shocking amount of overlap), he can force a favorable matchup vs BP.