Can't understand the TH/SS Belail. We only have 2 ways of getting I5 into the army (the 2 ICs), bith of which can wipe out 4 opponents (on the charge) before they get to hit you back.
The TH/SS is simply 'more of the same' which any 43 point model in our army can have (and generally does have as standard), so why waste one of the only I5s we have. The jump from 5++ to 4++ really only becomes relevant after they've attacked, with TLC or SoS Belail's done his job (and generally failed

) so if he dies, I don't really care that much (the very fact he's taking those armour ignoring hits means that my squad isn't, so he's doing another useful job). Also, without eternal warrior opponents tend to chuck a powerfist at Belail anyway and a 4++ isn't a great deal better than a 5++, were it a 3++ I'd consider it, but probably still not take it...
As to 750 points lists, they are tricky as you'll always have points left over because of Belail. I don't think you'll need chainfists at that points level so I'd go:
Belail - TLC or SoS - 130pts
Shooty squad - AC - 245pts
Shooty squad - AC - 245pts
Dreadnaught - AC,DCCW, HF - 130pts
Cheap & cheerful.