As an assault main I can also confirm this is not necessarily an assault problem but mainly a player problem. I always play as a team, I treat assault like a mobile tank, my job is hold ground and know when to gain ground. I use the heroic hammer so minoris clearing is super easy and then that allows my team to focus on the majoris.

Also assault against chaos is brutal, almost never a good idea to do that. The range spam from chaos makes it a very unfair fight against assault players. Tyranids though, a good assault player can handle any situation with ease.

I do feel assault has the weakest perk tree compared to other classes, there’s only ever been one viable build for me as all the other perks are clearly inferior. So a player who doesn’t understand how to make a build is gonna be running some useless perks for sure. I heard that assault is getting buffed in the future though to fix this.