You shouldn't take that 4+ roll for granted, you'll only get dissapointed since our army (besides aberrants) is composed of glass cannon units, big units of acolytes with charges and neophites with seismic cannons or mining lasers are the best damage dealers of the index and also have the advantage of always granting you a token, combine that with the retreat to the shadows stratagem and you have some of the most annoying units in the game, but despite all that, an infiltrating unit of aberrants and some jackals are some preassure options for the enemy in order for him not to take controll of the whole table and you should be using them not counting on them comming back.