Best advice I can give you based on this info is to run a 4-4-2 comp with groups:
Group 1: Druid, Ele, Ele/Necro, Warrior
Group 2: Druid, Ele, Ele/Necro, Warrior
Group 3: Chrono, Rev
There isn’t really much reason to take two chronos. One can provide good quickness and you can bring another DPS class as well.
The most common comps I have seen for xera take 4 elementalist or 2 ele + 2 necro as the damage dealers. Eles deal better damage but necros are easier to execute since they are tougher to kill, have faster CC, and completely trivialize the adds with epidemic and CPC. Using a thief or guardian as a damage dealer is fine as well, especially since they have good CC, but you’re going to want at least 2 staff eles to deal with the bloodstone shards. Overall this fight is about survival, since the DPS check is one of the lowest in the game, so play defensively if you are having trouble. Bring extra CC, play full healer druid (i.e. magis/clerics gear). Bring two druids – even if one is enough for healing, two makes it so much easier, and it ensures that everyone gets the ridiculous druid buffs from grace of the land, spotter, and spirits.
And for god’s sake, everyone besides the tank should stand behind Xera. You don’t really much any information about what’s wiping your squad, but if you’re bringing the brown bear it isn’t too hard to guess that people have been getting whacked with her confusion stacks. kitten the brown bear, bring an electric wyvern to break xera’s bar fast, and maybe a fern hound for extra heals. Make sure your eles keep bloodstones clear, even if they have to use meteor shower. This fight isn’t about high DPS, it’s about not dying to the mechanics, so play it safe and keep everyone alive.
Also make sure everyone stacks tight. If someone leaves the stack the adds have a tendency to focus that person, plus then they don’t walk into the AOEs near xera and die.
Hope this helps, good luck!
The support is decent, and you get DPS boosts with Grace of the Land stacks.