To win Maat Whm, you have to take his beatings for 5 mins AKA from the time you engage with maat. So if you takes too long to rest and rebuff after you enter, you won't have enough time to "beat" him, or take the 5min beating.
The way i do it and how i help me friend is..
1. Macro all spells , mainly Cure 3,4 etc, Paralyna, Haste,Erase, DivineSpell,Benediction, Vile elixir macro if you have it
2. Do not use medicine that prevent you from casting for next few seconds to 1min , i think super potion did that.
3. Wear the highest Def gears you can find, Druid Rope is nice (the one with -% spell interuption), Bat earrings are a plus with blind potion, a phalanx ring and Cure ring, and of course Earth Staff.
4. Yagudo is a must, Hi-ether is nice but rememeber it takes sometime to use it.
5. Food wise, i used steamed crab or boiled crab (lol), any with +def is nice.
6. Go in with blink and stoneskin and usual buff, cast debuff on Maat only at start, don't bother renewing it during fight unless you have enough mp.
7. Don't melee, it gives him tp , so that's a no-no unless you are trying to use melee style to win him.
8. Use your divine Seal and benediction as needed, they are there for a reason.
9. Only erase or -na, stuff that will disturb you, like Dia or Paralyze.
10. Echo drop is a must... i hope i don't have to remind any mage job on this item, but just in case.. <.<
Remember, the WHM maat is not taking certain damage to win, it is to take maat beating for 5 min FROM the time you engage. So taking as little damage as you can is the best way to go. Remember not to buff and rest for too long when you go in.
On side note, i did bring both Vile and Vile+1, but didn't use both. I used DS and Benediction, and almost have to use Vile before maat gives up

. I didn't use any kiting or special strategy, just go in, cast a spell so he walks to you and beats you up xD. There's a lot of chance for you to cure yourself since he use spells a lot. Best tip is : Don't be nervous, whm maat fight is funny... in my opinion xD.