I disagree with the premise of this thread. Vitor has knocked out three very worthy opponents all with head kicks. The whole thing took him like ten minutes.
TEN MINUTES. Michael Bisping, Luke Rockhold, Dan Henderson. All head kicks.
There is absolutely no coincidence that not one of those three men could mount any substantial offense whatsoever before getting their head kicked off their shoulders. I'm no Vitor fan but the fact that I'm pretty sure he never head kick KO'd anyone in his career (as far as I can remember anyway) and does it three in a row to high level guys...
Vitor has improved his game. He has not lost in 7 years (the last of which he avenged tonight). His only two losses in 12 fights since then were title fights at 185 and 205 against Anderson (MW GOAT and arguable GOAT) and Jones (arguable LHW GOAT and arguable future GOAT). He might always have trouble with these fast rangier guys who can wear him down with superior counters or wrestling (Anderson, Jones) but I don't really know what more you want him to do.
Of those 10 wins, btw, he won 8 by KO, 1 by sub, and 1 by decision. Again, not a Vitor fan here, but I don't see where anyone gets off acting like Vitor hasn't gotten better or something.
TL;DR - Yes he's shown us something.