If you aren't getting value out of his Q in a team fight, I dunno man. The Q talent at 16 ramps him up considerably, the Q in general is ridiculously easy to hit and he can still remain relatively safe, and the talent itself ramps up quickly once you have it. It's not a huge feat to hit two or three people with it every few seconds, on top of the one person you hit with the Q in between to keep it stacking. It tacks on a sizable amount of damage across the course of a game, along with the good wave clear.
The corruption talents are too unreliable for me, despite the amount of damage they do. I don't see any significant boost from the talents (outside of the level 1) that isn't achieved much more easily by the more reliable Q at 16 or going sustain talents. If the corruption talents didn't require someone literally walking in a straight line forwards or backwards to hit (and on a 16 second cooldown no less) I'd probably feel better about taking the one at 16.
As for dying, I've not really had a big issue with Gul'dan in comparison to any other hero. I average 2-3 deaths per game no matter what ranged hero I play, though. I find him to be considerably more tanky than other range heroes, he just can't escape like Li-Ming (til level 20 at least). I suppose you could argue that a completed quest KT is tankier or near thanks to the stun as well. When it comes to surviving someone getting on him, though, I find him far more resilient than most anyone that doesn't have a stupid OP movement ability. I've baited quite a few Zeratul's/Illidan's/Thrall's to their death thanks to taking Healthstone to combat the dive at 13, and they run in all crazy eyed to a half health Gul'dan and I pop Healthstone/Corruption/Drain Life and end the trade at 50% again provided anyone on my team is paying attention.
