For Ifrit, MRD can get comparable numbers to a LNC, although you may take slightly more damage. As has already been stated, Maim and Keen Flurry are nice, there will still be periods where maim is on cooldown, and, during that time, Brutal Swing II is just as effective. Brutal Swing on Ifrit avgs 200-300, Maim usually hits ~1k with buffs, so they are comparable, but Maim will on avg do more with the same amount of TP.

Once you know the WS's to use, it's simply a matter of building the TP. Broad Swing/FullSwing/Heavy Swing, are great for building TP, don't hesitate to use them as the damage is good. Invigorate is good as well.

For the most part, there have not been glaring balance issues with the classes. While there are definite and clear winners, they are not so far removed from the other classes. LNC atm is the best class for Ifrit, as you can avoid Sear, and the Damage is superior. But... the difference is not so incredible, and Sear is hardly an issue for any group that can clear Ifrit.