This is a really touchy subject...but I'll give my 2 cents:
Boss griefing is an option in the game.
I'm sorry, but that's how it is. Bosses are designed to be a challenge, and because of that, it's easy to take advantage of. Sulis has had similar issues throughout the years, where some people decide they want to cause trouble for everyone else on the server, and it's tough, I know.
Now, if people are decent and mature, there won't be an issue of griefing...and I think most servers are at least sort of peaceful right now. However, sometimes people just want to be jerks and mess with others. There isn't really anything Support can do, unless the griefers use glitches or get way overboard on the harrasment (especially verbal).
In response to your main question: generally boss griefing is looked down on by most people. It's not worth the drama that ensues (for example, this topic).
However, sometimes there are jerks who just want to ruin the game for others. Sometimes it's nice people who got offended by something, (for example someone in clan A messes with a member of clan B while they are lixing, then some people from clan B decide to grief all of clan A for a while in retribution). When that happens, the blame falls on the clan leaders imo...for not stepping in and telling the involved people to knock it off. But I digress.
My main point is, like it or not, griefing is available in the game, but any decent person won't do it. Because it's available, Support is very limited in what they can do...they can't really ban people for what is essentially boss competition. Now, verbal harrassment is a slightly different thing, by all means report that to support, maybe they can do something.
Griefing using in game mechanics like aoe is a grey area. If it starts to become harassment then that’s where actions would be taken.
I'd say these two quotes sum it up pretty well. In terms of griefing, it can be hard to tell with just a report. Videos work best. For harassment: I suggest y'all keep a file of what is happening in and out of the game. Take it to your local authorities and PM me the pics. There's only so much we can do but we can try to make it a better environment for playing.