Just to explain what happened in T11 in OPs case:

If all three nodes merge they get huge defense and hp regen while doing AoEs (3k damage maybe) non-stop.

You can't kill this uber node and it can't kill you (if you get healed).

But that's only how it looks. Eventually you will die to enrage or healers being oom. So OP wasn't really stuck, he was just dying a very, very slow death.

This is NO bug.


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Also I wanna repeat that OP is not getting why unsynch was even implemented.

The whole purpose of 'undersized group' option is precisly that SE has not to adjust any old content.
The issue of old content is accesibility (i.e. meet requirements like a full group at certain ilvl and skill level and specific roles) and with unsynch and cross server pf this issue was solved.
Every ARR fight can be cleared in a few minutes and you always find people for that without any problems.