Impossible Mode: Paladin Skills and Order

[Vulture]

The Paladin is everything else but "mixing [...] mass effects of the spell tree". The Paladin gets more magic runes than the Warrior, that's all. In order to use any AoE spells you need Higher Magic which the Paladin plain doesn't have in his magic tree.
You play a paladin practically like a warrior, just with a lower rage pool and a bigger mana pool, more healing power and with having Distortion leveled up to level 3 earlier in the game than the warrior can. With less leadership and attack (no 2 weapon slots, regalia instead of 2nd artifact slot) you will notice that tactics become more important than brute force.

Since you're just lvl 21 you're still in the nitty gritty areas. Those areas where the devs weren't pressured yet to release the game yet and had time to actually balance it and create quests. Once you're after Elinia you will notice that with 1/5th of the amount of quests (but equally rising enemy stack power) you won't level remotely as fast as your surroundings.
Your Geyser spam won't help you later on in the game, least of all on impossible. Plus hard is just slightly more difficult than normal. The differences are minimal there. Not so between hard and impossible.

Informations on cookie-cutter Paladin builds can be found all over this forum. The search function will be of service. Detailed breaking down of each and every skill in the trees with multiple opinions by players that have finished impossible campaigns (including no loss campaigns) with the Paladin.