Dom ops is really a poor choice to try to get seals specifically. As said already, you can only get 1 per day. And even then its completely random what job you get, and whether its body or hands. Doing a quest would be faster since its only 4-5? jobs, one armor slot, and can do it as many times as you want. But even still, NMs are easier and faster. Even without procs you are likely to get at least a few seals.

Many of the NMs in the newest zones are not particularly hard either, if you have a job that can solo (nin thf dnc) or duo/lowman well its really not that hard. Have at least a blm since they tend to get most procs and look at what you might be able to lowman. I usually go as dnc/nin for ninjutsu procs, my fiance who is brd/whm for brd and some divine procs, and if I can, drag along a blm friend. Thats nearly everything there except for blu. Add in a thf (or play it yourself if you have it) for TH and you can be finished relatively quickly. Its still easier than pre abyssea trying to get af2 for example, where you'd be doing dynamis maybe 1-2 week, need quite alot more people to do a run, and then hope your leader chooses the zone you want and then compete with anyone else who wants it.