not a lot of anti-tank to be honest, but then again you won't see many at a 650 pt game.
Also it's worth dropping the blast pistol, will most likely use it only once, so a bit of a waste of 15 pts. Trade that and 3 more points to give them all haywire grenades (and any remaining points to give it to your succy as well). That shiz screws dreadnoughts.
To fit a ravager, you can probably cut two of the klaivex powers, reaver jetbike unit (3 dies too easily, they work best in 6 or 9s, see Mushkilla's articles and BRs), and drop the flickerfield on the raider as you will be moving in at cruising speed per turn.
ravager, raider and haywire grenades, that should be enough anti-tank in such a small game. You are more likely to see dreadnoughts at this level. Others say that with 5 man warrior units, give them blasters, but really unnecessary as it requires them to be in a danger zone to use the blaster. Use this unit to do a last turn capture of objectives, whilst poking 12 shots per turn as many times from 36".
The two venoms should do for this size. Although the raider can be given a dissy to help pop a few heavy infantry dead prior to charging, at the expense of anti-tank.