Well, that little argument was HELP I AM TRAPPED IN 2006 PLEASE SEND A TIME MACHINE. There's two very different points of view;
A: Kill as fast as possible without worrying about grellow
B: Make sure you proc grellow
Except that the guy defending point A seems to think that the people defending point B are spending 10 minutes to kill a mob. No. As I already said, most of our fights were only 2-3 minutes, WITH proccing grellow. The blm has the biggest job, but if they cycle through T3 > T4 > ga3 > AM, and the other jobs are doing their spells at the same time, there's a very good chance that grellow will be proc'd before they get up to the ga and AM. After all, there's only a 25% chance that it's going to be a ga or AM. If you have two blm, or a blm and a rdm, then that cuts down the time even more.
As others have said too, the best you can hope for without grellow is 2 seals, which from what I've seen, you generally won't get even with TH4. WITH grellow and TH4, you're pretty much guaranteed to get at LEAST 2 seals. Basically, with grellow, you're going to get twice as many seals on average than you would without it. So at 5 minutes a mob (2 minutes to kill, 3 minutes on repop) vs 6-7 minutes a mob (3-4 minutes to kill), proccing grellow is a LOT more efficient. And again, even with proccing grellow, I don't think any of our fights lasted 4 minutes.
As for splitting up and killing multiple NMs at the same time, well, you're not really talking low-man situation any more are you? Unless you're sending out very specific duo partners to each NM.