I've been using a defensive Latias on my BW team, so many good resistances.
Latias@Leftovers (Soul Dew if possible)
248HP/68SpA/192Spe Timid
-Recover
-Draco Meteor
-Surf/Reflect
-Roar
This Latias stops most most speed boost Blaziken cold, as well as packs good resistances against sun/rain teams. Phazering messes with teams a lot. I used to use reflect, except there were not many pursuiters. Speed outruns non-CS-Garchomp, max HP, rest in SpA (or can be put in defense for extra defense there).
Not quite. This Latias is OHKOd by +2 Jolly LO HJK about a third of the time with Stealth Rock, while Rash 60 Atk Blaziken 2HKOs about a third of the time with LO Stone Edge, factoring in Leftovers. Definitely a check for the latter, though.