Is it me or is there a lot more c4 spam since the thermal nerf.. maybe its just my limited perspective. Has anyone else noticed the increase as well?
Sadly since the Oracle of Death stopped working in June 2016, it's been more difficult to answer that question without resorting to speculation or personal anecdotes.
Maybe you are just noticing it more because infantry isn't getting farmed from gals as easily so some of them are actually making it to their targets? I personally have always run c4 even as heavy.
It is possibly just that more attacks are getting through, or maybe yes - more people are trying it (or gone back to trying it) since it became less suicidal. Anything new tends to get spammed for a while (remember Valks, Tomoe, Medics since the KD change?) so maybe user friendly C4 is a current fashion trend.