First off, good on you for being a Pally!
Secondly, to target someone/thing, right click them. Your "target array/panel/thing" will now display them even if your cursor is not on them, and you can now cast spells on them. With my 14 CHA at Lv 2 I healed Heyton for about 24 HP with my 1/day Lay On Hands.
What I had:
+1 Power Plate
Boots of +2 Intimidate and +2 Diplo
Other Random Gear
What I did:
I ran forward, as far as I could go (literally walking in place with my head nearish the middle of the barrier). When the first wave spawned, I waited for them to choose their targets as my Axe flails about bringing a couple low, then Intimidated them to me, then QUICKLY tripped the largest one (because a caster was not in this wave for me; those are top priority) and then smacked them each once in a row until they all died (to maintain the intimidate, which, IIRC (from playing 3.5) requires the intimidated to be damaged or they'll stop being intimidated). Rinse, repeat.
1: walk in place on the barrier
2: Intimidate all enemies
3: damage each of them once really quickly
3b: Trip the Caster *OR* the Largest one (in that order)
4: Kill them all
5: Rinse, Repeat