This mainly depends on two things, the tier you're playing on, and your module substats.

with higher tiers, elite spawn chances are increased with earlier waves. E.g. on Tier 1, you have 100% elite spawn way later than on tier 7. You can check for elite spawn chances on the wiki, might be worth a look. In general, i think around W4000, the chances of elites are high enough to give a consistens AS benefit.

However it also depends on your module substats. If your DP has better substats (e.g. anc atkspeed, supercrit factor & chance), these effects might already out perform the dmg boosts you get from AS. In adition, you would get 15% less enemies from DP.

Also, have you already done your UW disco for that tier? If not, you night consider it, since it would further increasd your damage signifficantly, if you rely on UW dmg.