I lost a gorgonian to my bubble coral (LPS) awhile ago. The bubble stung it in several places and there wasn't much left in the way of healthy tissue left. Its all going to depend on the size of the tank and the type of lighting. Mushrooms can overtake a tank and pack a good sting. I saw a hairy one take out a frogspawn in a friends tank just a few months ago. You can mix gorgonians, mushrooms, LPS and softies with no problems though. Just be mindful of the placement of the corals. You should run a fair amount of carbon if you plan on stocking faster growing leathers to minimize the chemical warfare they unleash.
most softies will mix it up fine. I have bunched them all together randomly over the years and the only one I ever saw irritate other softies was Kenya tree, and that was less than what an Aiptasia would.
it's when you start touching softies and stonies, you have to watch. (LPS=stony coral like bubble and candy cane, meat etc)
mushrooms kill stonies if they touch. ...seen too many quick frag deaths. sps and LPS alike, and they kill them fast. you can have shrooms under stony colonies. it kind of works out because the shrooms like the shade so they lay low.
other softies and LPS are a "case-by-case" deal zoos seem to be fairly mellow WRT ticking off stony corals. actually zoos hardly fight with anything. i've had leathers bumping elbows with caulastreas and frogspawns no problems.