Sayha's seer is THE class of 1v1, random ganks, and still really strong in oly. But I found that lately, Eviscerators (that were already pretty strong with steel mind) became real monsters with the buffs they received in IO (plus enchant time on Steel Mind...). With the according gear, you are able to do some auto-attacks for like 15-20k on someone equipped R99 stuff, and if I had to reroll to one of those class, I'd probably choose Eviscerator. But that's two really different gameplay, it totally depends on what you want to focus on.
Yeah, now yuls are DDs. (Don't laugh, Yuls were low-tier DDs before) You need stuff, cause you don't have a lot of tools to keep your *** alive : you have the most powerful UE on the game (you almost cannot die in UE by physical dmg), but its cooldown is really long. Flash is basically a disparition (without the cleanse part) with 4x sec cd, you've your hide, and that's all (not speaking about revelation here, every class has them and their cd are long too). But you deal damage : A crit from pinpoint or quick shot will deal a really good amount of dmg (ignore 30% pdef, can be increased with skill enchant), flare is amazing against Yuls/Daggers/Sayha (and now works against unflagged ppl), the 2 dashes help a lot to kite/use the geodata to avoid being smashed to the ground. P.S : Don't have it yet (T.T) but the 101 skill of yuls is simply amazing (Ghost sentinel wins, for 1 min (cd 10, so about 5-6 min with +8 set/frint/...) +40% skill power, +20% skill crit rate, +40% skill crit damage. You simply deal a ****ton more dmg) TL;DR : Yuls deal dmg They need stuff
Evi is useless as far as PvP or even most PvE goes. Free hero if you have a clan backing you though. For yuls, either go DE ghost or DE and change to Trickster, that would be my advice, the two are best for now. Seer, as the person before said is perfect for 1v1/gank/oly, if that's what you're looking for and isn't hard to play either.
GS is the best, followed by trick, but if ppl think a little, MS with proper dex setup + skill crit stuff is a gattling gun of crits. Saggi, if u stack p attack, your damage gonna be osom too.