I honestly don't get why people are complaining about Onslaught so much

I've beaten at least half of the Onslaught games I've played, it really isn't as obscenely difficult as people are making it out to be. Focus down the Vel'Koz and you're pretty much good to go. During final boss, the actual boss itself barely does anything harmful and all of its attacks are extremely telegraphed and easy to dodge. Just focus on the mobs it spawns and it's not too bad.

The amount of people I'm seeing say "IT'S IMPOSSIBLE" or "NOT FAIR" is just absurd. It's challenging and I think it's a fair challenge. I for one am having fun trying to do the restricted runs with friends like not being allowed to have supports and stuff.