If you run as whm in dungeon then you should know that you only need 30% of your mana to keep the team healthy
The 70% left are dps

My best advice is to teach new dps how to be and how to place themself ti make it heal-friendly
Like :
Ranged dps should be as near as possible of melee range because there is no point for them to be away
And it allow you to use cure 3 and asylum to heal with minimum cost

...

Don't be afraid to let your tank health go down to 30% (if he rotate CD it should take a while to reach that point) them use tetra and regen and you can CS again
Also do never hesitate to use and abuse benediction i mean... Free ultimate heal with no mana cost
So perfect

Whm got the most stronger burst so you should be able to cover up for your friend until they got stuff.

BTW if you have some Crafter try crafting some 220 piece it's cheap and easy
And real good
Because only lore stuff is better