The best support is Thaumaturge if you’re willing to invest in your character gearwise.
You can even go as far as building a full support Wizard with Thauma3>Chrono3 or Linker2>Thauma3>Enchanter2.
Cleric doesn’t offer much in boosting damage, I guess the best option would be Cleric3>Paladin3>Kabbalist3 simply because you get level 10 Divine Might, Fade/Guardian Saint [depending on your preference], Sanctuary, Barrier, Double Chance & Geburah.
The damage increase of Divine Might, Double Chance& Geburah is a lot more gimmicky, though, because it doesn’t provide such a huge & continuous boost as Thaumaturges +2000 - +4000 matk do,though.
The only similar boost that Cleric can offer is Paladins Sanctuary, and it has a lot of downtime, so I guess Thauma is still the better option, especially if paired with Linker&Enchanter.
What people tend to forget: Merkabahs Divine Protection attribute also provides a chance to evade magic attacks while near a chariot, similar to Murmillios Cassis Crista, hence the name of the attribute: Divine Protection;
it is the main effect of the attribute.
Merkabah also draws a lot of aggro when summoned, with each chariot having its own aggro limit, unless the summoner is using a quest that generates more aggro to mob monsters (like me e.g.);
In this case Merkabah does not draw aggro since your aggro is higher, even if your monster limit is already saturated.
This also applies to e.g. Geburahs aggro effect, it will not aggro monsters towards you if you’ve already reached your aggro limit with this type of quest active;
Or if your friend/party member has such a quest running for easier mob control/influx.
Kabbalist is not a SP-battery/accumulator. And reducing Ein Sof to it is pretty sad.
Ein Sof is a survival skill that’s supposed to increase the max HP & healing capabilities of people, to recover SP people have to start investing in SPR and pots instead of crying for Ein Sof as if the SP recovery was the basic effect of the skill.
I only use the SP recovery when soloing to save ressources, otherwise it’s far better to have 4,2 times your natural HP because people still die in PVE although it’s so pathetic damagewise simply because they don’t use pots at the right time& don’t spend a single status point in CON.