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Since one can only use 1 power per player turn, is it a waste to give Zoanthrope both Wblast and Catalyst?
Catalyst is one of those powers that's only situationally useful. In most cases, the Tyranids will be striking before (or at the same time as) most foes anyway... with a few exceptions (Dark Eldar, in particular). I rarely find the boost from Catalyst is needed on anything but a CC Carnifex (and even then, only rarely).
A good solution is: 2 Zoanthropes with Synapse and Warp Blast, and 1 Zoanthrope with Synapse and Catalyst. This should provide you with the same utility as a WB/C Zoanthrope trio, since you shouldn't have too many broods that need the Catalyst boost anyway and you still maintain 2/3rds of your potential shooting power.
I see Catalyst as a 5 points per unit frag grenade option. My gaunts are usually charging into cover (normally against everyone who knows what they are doing) and paying 1pt per model for the frag nade (flesh hook) is a bit expensive when it comes to horde army like us. :x
Well where is the rule that you can use only one per player turn? I cannot find that any where in the Main Book or the tyranid book.
One power per phase i can see, since the Catalyst power is in teh assault phase and the Warp Blast is the shooting phase, i'd say that the two of them could be used during the turn.
Personally, I use Gaunts the same way you're using Catalyst... to remove an enemy unit's cover bonus before I hit them with something actually dangerous (like a Genestealer brood).
Aye I agree with Poptarts on that, Hormogaunts are the Genestealer's frag grenade!
Never heard it put better.
I've never used catalyst before, but that's because Warp Blast and Synapse are both so important to me, there's no room for anything else. I've heard good things about psychic scream as well.
But to answer your question, I actually think that you can use both catalyst and warp blast in the same turn. I couldn't find it in the rules book either, but I would say that since they happen in different phases then it is good.
Tyranids: 2500 pts
Imperial Guard: 1000 pts
Witch Hunters: 1000 pts
Heheh, I like that Homa-nade thingy for the Genestealers, a frag nade that actually inflicts damage.
About that 1 psychic power thingy, I've asked it in the rule forum with the specific example too.. here's the answer:
http://www.librarium-online.com/foru...ic-powers.html (Number of Psychic Powers)
Not too appealing
Psychic scream makes an excellent second power. No roll to use it, so it doesn't get in the way of the first power, and it's cumulative. Three of them means a -3 Ld. On top of the obscene outnumbering that Gaunts can do, even Ld 10 squads are looking for ones and twos on their Ld dice.
MEAT IS MURDER
Well Nekochen, untill i see an official ruling, i have to agree with the others that state, to go by the codex . That or do Nagato's suggestion.
Don't ever put Warp Blast with Catalyst on the same zoabthrope. NEVER! you can only use one of them each turn. You could better have them take Synapse and something else. This way your zoanthropes are also better protected from harm or the insta-kill tactics.
Tyranids Win / Draw /Lost 
Daemon Hunters Win / Draw / Lost