I suppose that most montages should show some interesting single-kills, multi-kills, or good killstreaks; and either using lots of skill, getting lucky, or showing off awesome teamwork.
Montages of single kills aren't bad, no, but there should be variety in the weapons or play styles at least. As it is, generally people are going to get kills, and thus be able to put each one together in a montage.
I suppose there are places for both types of montages; the single-kill stuff for showing off the game to friends/family and subscribers, and the long special kill videos for showing off skill.
At this point, there are some of both types, though there ARE getting to be more of the former than the latter. This early on, we need both to grow the community, and as it grows, the crazy kill-based montages will come to turn the nonbelievers.