A 2500 GK army can run Coteaz/Libby, 5 DCA squads (3 in crusaders/2 stormravens). Steal initiative with 1/3 chance due to Coteaz or turn your steal into 1/36. Move all the vehicles together and pop smoke then throw up shrouding. Armour 14/14/14/12/12 with a 3+ cover. You don't see too many pure lascannon squads of longfangs and even if you did they only have a 6% chance to wreck/destroy a shrouded crusader. Noone does landraiders better than GK's now with str 7 rending assault cannons and str 5 hurricane bolters+fortitude to ignore shaken/stun. The nades on the crusader allow the DCA's to strike at I6 and that list can squeeze out 3 techmarines to add defense nades/-1 toughness and pyschotroke (nasty effects if you haven't read the book).
I'm not too suprised that you haven't seen many of these list because most players will want to run a more pure GK list with dreadknights and paladins, etc.. but I think the henchmen list are much nastier if done right.
Our psychic defense gives us a much better chance to prevent their big strength boost from hammerhand and might of titans but that army will be assaulting by turn 2 and I've yet to find a unit that can stand up to DCA. Yes, I agree you have to find a way to bust vehicles and shoot/flame them off the board but that's easier said then done.