Adding a kill limit: As someone already said, it can end up being feed by players who enter only for medals and are not geared
Adding a life system: I don't think it's a good idea, since if someone from your team gets dc, you lose 3 lives already, and in the case of making a "group life system" I would make those people without gear who farm medals use again most lifes, feeding and making his team lose.
Increasing the HP: Currently there are many active healers in 10vs10, and that would only make them immortal, nerfing the healing would not help to solve this problem at all, for example sometimes 4-5 healers come out of a side, and 0-1 healer on the other side, in that case the nerf healing would not affect 4-5 healers together even more if they increase the HP, the opposite of the other team without healer would be affected by being much more difficult to kill the healers
Lowering the match timer from 6 mins to 3 mins: The current 10vs10 time is not 6min, it is 12min (which I think is a bug since last patch / maint) and that's the biggest problem, I've spent 36mints in an arena, and really boring and sad when a 10vs10 arena lasts longer than a gvg, even worse when there are troll that being aware of the 12min bug only become invisible all the time or templar rats that only run spamming their racial cure to make time, now in the case you alpaca in 10vs10, you have to wait for the defector time, and 30min + in a row for the current time of 10vs10, which leaves you doing only 3-4 sands, it was really fine when the 10vs10 time was 6min .
I think it would be great if they reduced the auto revive time to 15-20sec (Actually is 40sec approx not sure at all), and set the time per round to 5-6mint again, since if you can't make a successful reagroup and comeback in 5min with that reduction of the automatic rev, then it is only a waste of time and it would be better to finish the round.
Another suggestion would be to shorten the defector buff time to 5min, and as I have already seen Jordan's response to this in another post saying that the purpose of the defector is to stop people just rage quitting or leaving, i would say its so much better than those people leave / rage quit in arena than only afking for rage, also Jordan replied that it can be shortened that why this suggestion
Increasing the HP: Increasing the HP and nerfing a bit the heals sound good, but u still forgeting classes like templars, this change would only benefit them by making them more immortal.
In general I don't think that 3vs3 needs any big change, I know that many people complain about the ilu and its range, but in the same way there are rangers with the same meteor shower range to cover the sand and kill an ilu, more if it is invisible For the bonus of dmg taken, abt ilu dmg I know it can kill you in a kd, but the same happens with a good temper, they can kill you in a kd too and nobody cries for that, giving them more hp will only make them immortal and if they are rats will only be endless, of course there are not many good tempers with decent dmg, only 3-4 in 3vs3, but the same thing happens with the ilu, there are only 3 illus with grimoire and one of them uses lv60, the others use staff which It should be enough m-atack nerf already. The problem here is ppl dont know how to counter another class, this is the fault of the players, not the classes, if there was a test for 3vs3 this arena would be less populated than MBA.
Changing Class: I really don't think it's a problem, if they can change class having started the match it is the enemy team's fault for letting them change class, the only situation in which it is not their fault is when they are under sleep (but still under sleep you can also change class for example to shaman and revive, which has already happened several times), I know that many times they throw sleep, change to cleric and revive the whole pt, but then the problem is with the "sleep" not With the "class change", I have seen a suggestion about reducing the sleep time, I think that making the person who sleep and who was under sleep continue in combat would be the perfect solution without affecting the class change that can be done. out of combat.
Also immune potions should be removed, lately there is a lot of random using them, it only makes classes like MA, engi become useless when using antistun for example, the same with a warlock if they use antifear, I know there is still the problem of use bard antisleep before the fight starts and change class, but that's something both sides can do, and otherwise make a rework in bard antisleep, make it a personal buff that gives antisleep to friends in x feet, not a groupal buff, something like HS antifear buff ( Aura Prophet Blessing: Ninini, additionally party members will be granted "Fear Inmunity") its a personal buff which put antifear in ur team but if u change class then your buff( Aura Prophet Blessing) get removed and not more antifear for pt.