I am a casual player, and i like group content. But being on a group boss, that's over in less than a minute and people shouting on the group chat things like "Cmon, let's get to the next one quick!", it's just not fun imo. And i can't find groups with less then 15 people to do a boss with and keep it fun and challenging.
Graglorn in the other hand is completely different, i came to this game late, and can't really find people to complete graglorn with. I hope i someday will, at least to that degree that i can open to group required door and finish my quest. Same applies actually to IC, i'd like to explore to area since it looks interesting to me, hunt down the bosses with my friends, but other players ambushing and only interested grinding are ruining our fun in there.
Granted this isn't ZoS's fault, as much of the players who are in only for achieving fast/rushing through every day, but there's a lot of us players that would like to enjoy the game and explore (in my circle of friends at least), for example Imperial city without being run over by a groups of people all the time since we don't have 10+ friends to roam there with, and don't have the chance of spending hours in a day ambushing and sneaking. I'm all up for fair fights like 2v2, 2v3 etc, but as a casual player 2v10 and more is just impossible and takes away the fun.
I pay for them, i sub, i want to enjoy them. I think i have waited long enough to enjoy the Wrothgar bosses, but no, i still can't. I wuoldn't want to wait till next dlc to get a proper shot at Wrothgar bosses.