Tactical squads on foot sometimes work but that is a completely different list. Also mixing heavy choices is not so much fun. Now back to the
OP 
.
Assault squads are just bad. Your sternguard is too expensive to be caged up. Lack of melta coverage. Vindis work best in at least pairs.
El Captain is not being used in the list. Termies will want a big gun. The dread doesn't quite gel in the list.
You have plenty of options.
Swap the assault squad for a vindi seems a nice swap.
6 sternguard, 4 combimeltas 2heavy flamers.
tacs with melta,combimelta, missile
or
6 sternguard 4 combiflamers, 2meltas
tacs one with flamer and one melta.
Would give coverage with vindis running forward. Combimeltas on
tac. squads are expensive but worth the points when in a rhino and able to help take down some mech just when needed.
Maybe for the elites if you made your dread a rifle dread to provide long range support then he would not be left out of the action. Then maybe swap termies for another
rifledread or giving them
CML to also support long range moving fire support would be good. I know you have
AoBR but the arms for the dread and
CML can be found cheaply enough online.
Librarian is a better standard
HQ. The captain is good to get access to command squads for example but otherwise the librarian is just better on the battlefield.
Hope that helps

. good luck.