People are way too stuck on FL. FL you could drop most regen and be fine. Besides HM Rag really, you could run with a full throughput spec if you played with a good guild.
DS isn't FL. Don't make assumptions off reg modes 1st off. Regs mean nothing. People are pugging and clearing regs with terrible players with only madness really giving them any trouble. Especially 10s. I've pugged 7/8 10 DS on my alt with a bunch of mediocre players.
In FL, you could spam pretty much anything with no mana problems. Throughput > regen because you just didn't need it. If you went full throughput, even with blanket RJing you really didn't have problems.
After the WG nurf, blanket RJing is pretty common. We're having to use more spells to keep at the same level of throughput we put out before. In DS, it's pretty pointless to run anything outside of 2/3 furor 3/3 MG unless your guild is casual and stuck in regs forever. In that case, it doesn't matter what you run...
So yes, this tier in HMs using full regen is better than dropping it for throughput on the majority of fights, which is what you build your spec on. T11 wasn't T12. T12 isn't T13. You can't base things off what you did last tier, because shit changes. The amount of spells we have to use now, the length of fights, the type of dmg/mechanics going out, and our niche makes more regen better.
Once everyone is way overgeared for the fights, this may change. But as of now, it's not the case.