ok, quick rant then I get to the question.
What they are going to do with resist will totally unbalance pvp yet farther. While it will help mages greatly, us warrior types already have well over 40 in each resistance, making it essantialy worthless. Now then with a skill that difficult, that really irks me. I think it should be a minimum bonus of a far lesser ammount. (like +1/5 total skill to all resistances. That would be much more fair) Ok! Now to the question!
Poison- Its expensive, it takes ages, and its as boring as it gets. Its also great in pvp and pvm, and is about as good a finisher you can ask for. The cost thing is not all that big a deal as there are many alchs here in the guild who would make it for you for nothing more then the nightshade involved, but trust me, make sure you have lotsa time and patiance for this one.
Resist- Barring my previous rant, this is, or was, a great skill. Presonally, i would wait till the jury comes in to make a descision here, but I presonally will not be droping it until im sure they are on a final answer. On a side note, this is one of the tuffest skills in the game to gm or gm+
Hiding- By far the easiest and cheapest of the three, its a valuable skill in a jam. Its one downside of course is that its essentially replaced by a spell that you can already cast with ease, and the spell never fails even if they are standing right on top of you. Another down side is that house hiding is just as easy in pvp, and requires nil skill. Either way, to make this call you really need to consult your game style more then anything. When I was newer I loved this skill, because when things got heated, just break line of sight and all is well. Now Im not saying its a newb skill, im just saying its great from pulling yourself outta the fire when you bite of more then you should have.