First off, I know how us BA players adore our Mephiston, but in all honesty, he is what I like to call the most efficient point sink. He is wonderful no doubt, but in any game size, he just soaks up WAY too many points, I'd definitely drop him.
Again as red orc stated, take Lemartes, he's awesome.
And again, since you have the death company, assault termies aren't a necessity, I would drop them hoenstly, make that CC dread a Las/Missle Dread, throw in some MM attack bikes, specialize that Vet squad, either the flamer or melta, and from my experience, Lightning Claws are another point sink, just go with a second fist.
These are just ideas, dont feel threatened by any of this, i just hope you can see where im going with my post and possibly allow me to help you
BTW, I love vindicators