It's a very good strategy, Lady C, but keep in mind the mechanics issues with it. The opposing group will almost assuredly attack the healers/master mage. At least if they are smart they will. One or two tanks will simply run through your fighters to get to them. With mechanics, it's hard to try and click on a moving character, so you shortcut /target next player. Well, if there are 10 people in the groups... then you may have to run through 10 shortcuts to actually hit the person who is running at your master mage/healers to try and save them. I still think it's an awesome idea, but just keep that in mind. You don't want your mages and healers to be wimps. I'd recommend having them train armor, and get them used to walking while casting. You'd be surprised how hard it is to hit a mage who is casting on you and simply walking in an erratic pattern. You can practice this while walking and fighting something that takes a while to mage down. I did it with neotens and imagoes when I was bored one night. Learn to walk out of their target line or die. XD
I've played in a lot of informal group-duels, where we did /challenge to each person, simply so there was less of a chance of killing, and there seems to be two main strategies people use in PS:
1. Nail the weakest links first so you can concentrate on the better fighters. [Honestly, this one tends to fail.] Many times, I was the weakest one on my side, and they kept coming after me. So, I ran over to circle by a stronger fighter, letting my stronger teammate target the offending bozo and kill them. XD
2. Nail the strongest fighters, so if you survive, you can't be beaten by the weakest link. I find this one works a LOT better, if you are mechanically capable of defeating the stronger fighters. With the new 200HA and 1600+ HP, it can be hard to kill some of these tanks. Even 100+ in a weapon doesn't let you hurt them AT ALL if they have 160+ HA. So, your mages would totally come in handy here.
Another thing, outside of the Champions Cups, and guild wars, you aren't likely to find too many people who like magic in group duelling. As the chance of death is astronomically higher. But, with the /groupchallenge command, you die anyway, so that shouldn't be an issue.