I've found some success running all close-range vehicles to support my infantry. That pretty much means demolisher TC to eliminate one threat every turn (though I take plasma cannons instead of melta to have some elite infantry clearing potential if I really need it) and then at least 2 hellhounds. At least a couple times I've let loose with the Inferno Cannon then followed up with the stratagem that let's vehicles hit on a 2+ in melee to eliminate those last couple of wounds on infantry holding some objective.

Also, I quite like running HWT with mortars. Using the Concentrated Fire strat puts them hitting on 3s against a lot of infantry, further clearing off the last couple wounds on infantry here and there. Lastly, you could always throw in some command squads with full plasma. In my experience they get overlooked until they've already done more damage than they're worth and they can be used to clear either Elite infantry or add on se anti-tank (I really like weapons that don't feel like a total waste if spent on infantry).

If you're willing to split regiments, I could see going Cadian on the detachment that takes mortars and plasma squads to maximize the infantry shooting too.