While an Auto-Refresh trait would be nice for WHM, it's far from needed. Abyssea has several forms of Refresh atmas, so I won't go into why it's not needed in there. Outside of Abyssea though it's different, and the main problem people seem to be having is realizing that WHM in Abyssea is vastly different from WHM outside of Abyssea.

Outside of Abyssea, you sub Scholar, you keep Sublimation up, you downgrade from Cure V and VI to Cure III and Cure IV (using Penury if you absolutely must use Cure V; never use Cure VI). Additonally, you rest. You get down on your goddamn knee if MP gets low and recover it the old fashioned way; in these situations you employ something called an hMP set, y'know, those things that say "MP recovered while healing +X"?

There's also no reason you don't have several ticks of Auto-refresh from your idle set. If you play through quests correctly, there's no reason you can't get at least 5mp/tic back. Let's count them off:
Weapon: Owleyes (+1mp/tic)
Moonshade Earring (+1mp/tic)
Body: Orison Bliauld +1/+2 (+1mp/tic or +2mp/tic respectively)
Hands: Serpentes Cuffs (+1mp/tic at night)
Legs: Stearc Subligar (+1mp/tic)
Feet: Serpentes Sabbots (+1mp/tic during the day)

Add it all up and you have at minimum, 5mp/tic (6mp/tic if you have the +2 version of the Orison Bliaud) return, and I'm probably forgetting about one or two other things too.

More MP is nothing more than an excuse to let a WHM act a little more recklessly; it doesn't (shouldn't) have any affect on their ability to keep a player alive through a battle.