ok.... i've given it some thought, and here's what i'm thinking for a badass finishing unit selection.
HQ- Librarian epistolary (null zone + force dome) - 150 pts
HQ- Inquisitor lord, 2x mystics + acoylte, in a land raider - 315 pts
Elite- 3x rifleman dreads
Troops- 2x squads as you described
Fast attack- 9 vanguard, 4x lighting claws(1 per model) relic blade and power fist in a razorback - 345 pts
Heavy- 3x dakka predators
comes out to exactly 1850 points... a little light on scoring models, but they aren't really there to kill things. the cool part would be that the vanguard + librarian take the raider bought for the
HQ, and the inquiistor could take the razorback the vanguard bought.
i'm sure the vanguard, with 18 lightning claw, 3 relic blade, and 3 power fist attacks on the charge will do some serious damage

and with the force dome from the librarian, they are almost as surivable as terminators. If you really want them to tackle things like nobs, they could always swap those claws/relic blade for 3x more power fists, and be about as good in hand to hand as a 5 man terminator squad.