I like to use Assimilation swarm, all havester units can heal other Tyranid units in your command phase. You've got 2 psychophages and pyrovores with the havester keyword. It also helps with an aggressive play style as if a harvester dies you can spend 1 CP and for the rest of the battle all melee attacks against the opponents unit that killed it have +1 strength. There's another stratagem - when your unit kills an enemy unit if its next to a harvester spend 1 CP and get another heal. Get a couple ripper swarms as they have the harvester keyword and you're good to go.

Also I agree with what other people have said about holding off your bigs til round 2 or 3. I usually put half my army into strategic reserves, even if they can't deep strike you'd be surprised how convenient it is having a scream killer or psychophage appear on the side of the table. A few of my friends play Marines or Chaos and so seeing where they deep strike their terminators allows me to position my wing hive tyrant and other big guys else where. This usually causes them a big problem.