Warhammer 40k Tabletop XXI: Preferred Enemy (Dice)

[Cheesegear]

The other option I'm considering is drop the two ten man squads and the Havocs, and take a big blob of Marines with the Icon of Vengeance and a Forgefiend. Or have a big marine blob plus the Havocs.

Nah, don't pick up a Forgefiend. You have no other Vehicles to draw heat. If the Tau or Guard have tank-busting weapons, when they wonder what is most efficient to shoot at, they're going to pick the Forgefiend, and that's bad.

Might not be an actual superheavy. It's some sort of Forgeworld model and I know it has a Str: D cannon.

Could be a Cobra, Scorpion or Lynx. The first two have AV12 and 9HPs. The Lynx is AV11 with 6HPs - but it's also <500 Points. If you're able to contact your team mates, you should make it clear to them that they need to bring anti-tank stuff, because you're Tyranids and you don't really have that kind of thing. But, you can focus on killing Infantry. If it was 1v1, then you'd be screwed. But Apocalypse games aren't 1v1 affairs - and nor should they be. The key to winning Apocalypse is communication with your team, and that includes before the game even starts.