Well, I've always been an MA lover. Even before the HP boost, I preferred it over HA, and why?
Dodge Bonus. A well crafted MA set has the same dodge boost as a standard LA set (+1 per piece). For a dodge tank, that is one big reason to use MA ove HA. The lower malus is another one. Losing 1000 HP compared to HA (if you can wear 250 HA that is... I can wear 250 MA, but not HA) only means 1 extra hit from most high-end mobs you'd survive.
Of course, for nameds/bosses/other nasty things (kinchers for example) you'd wear HA most likely for the extra HP and PF, or you're a goner. But for regular grinding? MA for dodge users, no doubt. Parry users will of course almost always be better off with HA (not too hard to get a nice parry bonus) because with the same recipe, MA will have +1 parry, whereas HA will have +2.
For maging, I frequently pair up with an elementalist when working my affs, and then it's very handy to be in MA, since I can't dodge while casting/linking. So, the extra protection helps a big bunch. As does the extra HP. And before you say I'd drain sap too much... false. If you open the "Active Links" window, you will see that the sap drained per tick to keep up the link is the same in MA and LA.
Personally I have the sap reserves to last an entire fight when afflicting (AoD

) but if this shouldnt be the case, have your MA made with sap bonus. At q250, that means 625 extra HP and 625 extra sap, compared to with LA, you'd only have half of that, or only HP/Sap.
And then of course there is ele tanking. Same as above, but you will ofcourse drain much more than with affs. However if no dedicated tank is present, it's the next best thing since an ele needs to be healed anyway, might as well make it less hassle for the healer(s) and let them keep one person targetted. The ele will more often than not get the aggro anyway so thats another reason.
In short, the limits of MA have yet to be found. If used right, it can be a very powerful tool
