I never understood the Coyle hatred until the 75% sale and I bought Threnal. I'm embarrassed to say that on my first attempt at protecting him on my lvl 20 PM I had no idea what to expect and he ended up dying. I mean one second he was alive then he goes running off and died. He took some damage before and I scroll healed him, but this was insta-death and he was buffed to the hilt. Next time I knew better though and had him knocked out and surrounded by disco balls, but it was boring. 15 minutes is too long. I can't imagine the horrors of trying to do this at level.
Each pack has it's own hated moment though for me. I didn't hate all of Threnal. Just Coyle. I mean the rest was nothing to celebrate, but one quest made it suck. In Necro III you have the lovely Tomb of the Tormented and the stupid boring rat maze. In Necro IV you have Inferno where someone always gets lost. In the Vale the Coal Chamber.
However for me on Cannith, it would be Restless Isles. Finding the quests is a pain. The two pre-reqs for the raid aren't bad, but getting there sux. Then trying to get a raid group is impossible. It is very rarely done on Cannith unless it is a guild run. I'd say I went a good 6 months without seeing a single LFM and I was playing pretty frequently during that time. Then a few came up and the pre-raid run took forever to do with only 2 people knowing what was going on, people getting lost, falling in lava, etc. Took an hour for the pre-raid and then of course no one knew what to do for the boss. Needless to say in a 2 week period a bunch of Titan runs popped up which I joined because I hadn't done them in a while. All were failures. All that hard work and the titan can glitch over away from a pillar or something silly. Then despite the fact you're all alive still it's a fail. A horrible mechanic with bad luck being a big factor as opposed to any skill or build type helping and you also have only 4 people doing anything and the rest piking on the ladder. Fun. That was one of the first packs I bought because the gear drew me in (gear which I've never pulled) and it is my most hated.