Maybe 2 5man squads 1 melta and Vt sg with pf. who are drop podded. Thats 300 pts. Throw in 2 dreads with regular armaments to meet his assault marines. Thats 505. Use your remaining 500 points to throw in the manditory squads and maybe a chappy. Assault marines die in sustained assualt, so keep your squads close and charge in to him with your dreads and with your tac squads. Drop pod the squads behind his dreads and watch him cry. 
