Having read so many threads on how to take a balanced tyranid list, I've concluded that it is very difficult. The primary problems are need for synapse, speed/wave problems, and durability of small creatures. What makes genestealer hordes and Godzilla (best list) so strong is lack of the two or even all three of the problems. I've concluded that a high amount of monstrous creatures is necessary for durability and anti-tank firepower. Genestealers are obviously needed in a marine heavy environment and are also pretty survivable with decent toughness and save. While having gaunts may not be necessary, they do add a speed and bulk element to your army that can help tie down enemy units. This should be pretty optimized mix of the three elements, granted its impossible to be perfect.
Tyrant - Wings, Toxin Sacs, and 2 Scything Talons
Tyrant - Enhanced Senses, Toxin Sacs, Venom Cannon, TL-Devourer, and Catalyst
2 Tyrant Guard
Carnifex - Enhanced Senses, TL-Devouer, and TL-Devourer
8 Genestealers with Extended Carapace
8 Genestealers with Extended Carapace
8 Genestealers with Extended Carapace
8 Genestealers with Extended Carapace
16 Spinegaunts with Scuttlers
16 Spinegaunts with Scuttlers
Ravener - Rending/Scything Talons
Ravener - Rending/Scything Talons
Ravener - Rending/Scything Talons
Zoanthrope - Warp Blast and Synapse
Carnifex - Enhanced Senses, Venom Cannon, and Barbed Strangler
Carnifex - Enhanced Senses, Venom Cannon, and Barbed Strangler
Total: 1849
I am packing a lot of anti-vehicle fire with the carnifexes and shooty tyrant. Should be able to handle skimmers (venom tyrant, dakkafex) and heavy armor (gunfex, thrope). I plan on playing a mini-wall godzilla style my carnis and walking tyrant and having my flying tyrant, raveners, and maybe a squad of stealers hiding behind the wall if there is no cover. Kept the tyrant cheap and effective against marines, didn't think spending points on upgrades was worth it. 32 stealers with good armor shall be pretty strong provided i can take down the assault cannon platforms. Termis and heavy bolter squads will still be problematic, but hopefully the faster elements can tie them down. Based on gorgon's analysis in the 'Nids Tactic thread, I decided to go with scuttling spinegaunts instead of horms. They will present a turn 2 threat along with the raveners and tyrant. Took the zoanthrope for the gaunts' sake in escalation and is useful against Monoliths and Landraiders. Catalyst is for the genestealers when they assault into cover and is much cheaper than spending points on frags for everyone.