It is hard for anyone to say without hearing your line array whether tapering helps or hurts your sound quality. Normally, my experience is to recommend tapering for mid-woofers because of interaction with the room. As you have a realively short tweeter line, you could still have room interactions at the low end of the tweeter's frequency range. Bottom line is that if the sound is better with tapering, then clearly that would be the better solution.

Jim