It sounds like you're playing purely PvM in Tram rule set facets, so my suggestions are based on that, they would be entirely different if you were playing support for Fel spawns. So correct me if that's the wrong assumption.
It would also help if you elaborated on which hunts specifically you're going along to? Are you with your own group or just helping out random people?
Reason for the first question is it affects how useful your support will be. If for example you were playing support at Paroxysmus' with the Provoke Mastery people are going to be Poisoned most of the time which means a lot of Provokes heals are going to be blocked. Same goes for anything that Mortals a lot.
Reason for the second questions is that Cleansing Wind & Bard Masteries are more useful in a party, and random players don't always want to party because it means you getting in on their loot/fame/karma, even if it's your own group on most bosses people drop the party at the end.
All that said I have the following comments for you to pick and choose from.
Melee defense. Read this post #4 to understand your own defense:
weapon defense
One of the Mysticism Masteries lets you have Mysic Weapon -5 skill for the same effect as a Mage Weapon but I'd also say that in most cases it's a waste of a Mastery.
Having multiple spell schools (Myst/Mage/Spellweaving) is ok if you understand how they all play together and what their functions are. The short version is Magery on it's own is all you really need to be a support healer. Cleansing Wind is essentially a 6th circle spell, and while it can remove a few curses they're less important than healing the damage, why this matters is because Greater Heal is 4th circle Magery and casts quicker, has the best range and heals for a substantial amount, which can be boosted further by Spellweaving, you also have Arch Cure for group curing which is more reliable than Cleansing Wind, the ability to Res, the ability to cast Wall Of Stone (if you're somewhere hectic you can block yourself and a ghost in to a one tile spot to Res safely), and Protection, I would highly recommend not playing in Prot all the time, but switch in and out of it as needed, it is much more beneficial to learn how to cast and time spells while being attacked, also has Dispel/Mass Dispel. Mysticism is a powerhouse of defense for yourself with a few things you can do for supporting others. From the sounds of it you know all about Cleansing Wind already, you've also got Stone Form, which makes you completely immune to Poison as in can't be Poisoned at all, stat curses, Bleed (I think), and gives you a nice boost to your resists so you take less damage with a few penalties to speed etc. You also have Mass Sleep which is very useful when you see someone struggling whether 1v1 or by a group you can unflag all the monsters from them, useful on spawns and selected bosses (like Semidar) but not much else. You have to also be aware that most boss level monsters counter attack, and their counter attacks are triggered by you damaging/cursing them. You also have Healing Stone, and Spell Trigger which you can set to Cleansing Wind for an emergency button. All in all it's pretty damn hard to die on a Mystic. Spellweaving again is hugely defensive, it has two great Masteries, Mana Shield which can reduce incoming damage, and Summon Reaper which has a nice area draw effect for distracting mobs. Attunement allows you to ignore an amount of melee damage, though on some bosses it also prevents you doing any damage to them while it's active. Gift Of Life can be useful sometimes, providing you aren't going to get Res killed. Gift Of Renewal is great for the fact it heals through all of the things that block healing but it also has a cool down and can only be on one person. Arcane Empowerment boosts the effect of your Magery heal spells, it's often better to switch to Lesser Heal when using it as they are so much quicker.
As for Bard skills. On most bosses Provoke itself is pretty useless but it depends where you are. For example if you were doing Ilshenar Champion spawns are Valor then it's very useful because there's a woods full of Parragon Greater Dragons to Provoke on the champion. The Mastery for Provoke increases stats and HP, based on real Bard skill points at 4x120 (Music/Peace/Prov/Disc) it is 23 HP which goes over the cap to give you 173. It heals you, your followers and anyone you're partied for that is in range for about 20 every 2 seconds, it is blocked by Poison/Mortal. Discord, most bosses shrug off most of the effects, but it is nearly always good to have a Discorder it allows everyone to have an easier time. The two Mastery's for Discord are also very powerful and allow you to get damage and rights while supporting the group. To sustain Discord Masteries I think you pretty much need 40 LMC, 120 Med and 30 MR on the suit, the damage is boosted by real Bard skill points. Peace, the skill itself is useless most bosses can't be Peaced. The Masteries, however, I would highly recommend for your purposes. They actively reduce all incoming damage, give an auto Cure effect for some levels of Poison (like how Vamp Form/orange petals do) and boosts all three Regens which also over cap and because it's Regen rather than healing it works through all things that block.
Other potential options you may want to consider are cross healing with bandages. Entirely different playstyle, you would need to maintain 140 Dex for the fastest bandage speed, which means it combines well with something like Stone Form where you can't have your stats lowered. Lacks range obviously you have to be within 2 tiles. Also 4/6 Chivalry, Close Wounds lacks range but it's fast and you can move in and out, Cleanse By Fire has great range, Noble Sacrifice redlines all your stats but Res's everyone in an area and I think Heals/Cures them too... if you were playing somewhere where you're not going to take any damage you could use Lich Form (for 13 MR) and stand there spamming Noble Sacrifice. It also has a very fast Remove Curse and Dispel. For your own defense Ninjitsu is also very strong, you can combine Bard skills/Masteries with Animal Forms (for example Prov+Wolf for 43 over capped HP, or Peace+Cat/Dog for 80+ HP Regen), plus Mirror Images. Like Mysticism it's near impossible to die on a Ninja playing defensively. These are more all out 'I'm just there to heal you guys' options which lack offense but all worth knowing to combine with other options to make something fun/interesting/useful.
If you're going with Bard skills, I'd suggest getting at least 2, either Prov+Discord or Peace+Discord. You could go 4x120 on Bard skills with 120 Mage/Med, or Myst/Focus, but with Myst obviously you wouldn't have any melee defense. Unless you relies on the Mystic Weapon Mastery which would mean not using a Bard Mastery (which kinda defeats the point). I'd suggest either that or you could do Mage/Med/Music/Disc/Peace/Spellweaving, Spellweaving gives you the added bonus of Word Of Death and is a great stand alone skill like Magery.
If you're staying with Mysticism, which I expect you are, I'd suggest using a Crystalline Ring as it has 20 Focus/20 Magery it'll give you a bit of freedom to do something with points wise.
Probably the best option would be Myst/Focus/Music/Disc/Peace/Magery. Get as many skill points on there as possible and put whatever in Med... if you can't get any Med you may as well make the suit non-Med and get 55 LMC.
