While I believe it surely existed before as well (just like with anything in this game) I don't think omen mercing was very common before they introduced Ou and the possibility to enter with more than 6 people.
Especially during the first weeks (which is the fair comparison we should have with Divergence in its current situation at the moment of this post) Omen was still tough, only pro groups were progressing and the majority of other people were wiping on the dreaded minibosses.
I know with my group we wiped/timed out on miniboss as well a few times, and while I'm not a particularly high-end player trust me the rest of the group was.
My point is that comparing the status of Omen now that it's 1 year old and received several adjustments to Dynamis who is 3 weeks old isn't very fair, whichever way you want to take the comparison, it's not fair.