General Help on Rogue casters:
Regarding your specific problem:
Offensive casting in catacombs is a problem indeed, even if one has very good gear one runs out of mana sooner or later usually.
As rogue caster you lack mana even more than a mage would do
Therefore, i see only 2 options:
If you decide to stick with offensive casting, it is better to play arena.
You can regen when needed, use shrinables and such between the mobs.
The other option is to switch your casting in catacombs to healing others.
This way, you can save much more mana and keep the party alive.
Between heals, you can still deal damage if you decide for a hybrid setup.
But not with a casting charm. In contrast, you go with an ee weapon then to save the mana.