I've been favoring tyranids (with ravener alpha), and I usually play team games with my two friends (usually another 'nid and a space marine). So far we've done very well in 3v3s, and very rarely lose a game without something like one of us crashing/dropping.
I was doing some 1v1s last night, and was winning all of them until I got into a game with an apothecary. He used the purification vials ability on his hero, and from then on I couldn't even bother to attack him or any unit near him with melee.
This ability is a bit too strong in my opinion, because it can completely kill a full gaunt squad the instant it is used. Now consider he can use it at the same rate that he uses his heal (the ability is tied to heal)--which is on a fairly short cooldown, and can be made shorter.
At least with a grenade-type ability (that'd cost some zeal or power separate from the apothecary's relatively cheap heal) I'd have time to run. Instead I see his heal flash, and I end up with (at best) 1-2 hormagaunts/rippers left in a squad, his units have just been healed, and there's a lingering AoE that'll finish me off if I send more units in or don't retreat. Warriors usually lose a unit or two and have 1/4 total life left at best. The only alternative is to completely change my strat to using ranged units, or completely avoid his apothecary (something that may work in a 3v3, but not in a 1v1 as this grants him too much easy map control, especially considering that the apothecary is not a slow-moving champion unit).
It seems a bit too strong--just getting one fairly cheap upgrade for a hero forces me to completely change my whole strategy (to a less effective one) and completely trumps tier 1--the place where a tyranid player absolutely needs to take an early advantage (we don't have a walker at tier 2, instead we rely on keeping our tier 1 force alive and preventing the enemy from getting too much power too quickly). There is nothing I have come up against like this.
I haven't seen how effective the ability is against ork melee. If it's anything like it is against 'nid I'm sure ork players would know what I mean (although orks arguably have some better range than 'nid, and are less tied to going either melee or ranged since their units do some degree of each and don't rely on synapse).
Anyone disagree/know of a simple way to counter this that doesn't involved completely giving up on melee (in my opinion the lifeblood of tyranids)?
If I knew ahead of time who I would play in a 1v1 and what hero they'd use, it'd be a simple choice to switch to a lictor or (yuck) hive tyrant--but since I never know who I'm going to fight, I can't adapt to them with commander choice, so please don't simply suggest that I should choose a different hero.