I've only encountered one I can be sure was hacking. I posted my experience in another thread recently, but TLDR: Someone was using I guess some sort of speed hack to be able to move around at crazy speeds. He was on my team, and used an Aerospray RG, which is a little merciful to the other team since even with that speed hack, he was getting splatted a lot. Towards the end of the match the other team had a good shot at winning, but we managed to still win, even though I sorta stayed back and just inked turf.
However, I had another match recently, I'm not sure if the person was hacking or not, but I swear they were using some hack to teleport around the map. At one point very early in the match, I was off to the side of Urchin Underpass (the little side lane behind the grate to the left of your base) inking like normal, when suddenly I was being shot in the back and splatted. I find it super hard to believe they managed to run all the way over to our side of the map, and slip past my three teammates like that to get to me. For the rest of the match, they were pretty much back in the fight very soon after being splatted, way too quickly to be playing normally. We managed to win the match either way, but it was still super fishy.
2 matches out of like 650 hours of play, I cant really complain about hackers on my end really. And it's nice you can just block them right after the match if you want.