BLM nightmare: You hit the group, he puts Ley Lines only to watch you running into sunset with the pack of mobs behind slipping out of his range.
Technically, if you have strong aoe in your group and healer can manage it, big pulls make it faster with decent aoe even if all you do is trying to keep aggro while dancing in a myriad of ground-targeted AOEs (Aery comes to mind).
If you have like two melees who have some aoe but not that much and having them to dodge all that aoe as well may just slow you down too significantly.

But the worst part of it is still that you put some stress on heals and dps because they're engaged in combat already but can't do anything until you stop... Which is quite unpredictable. And it may very well be you'll keep ruining their rotations constantly because one Very Important Skill which they planned to use cause they knew mobs have enough hp for this renders inaccessible at the right moment.