you can find Hero's Poise easily with the conpendium but if you don't have an account with WoC I have it here for you.
Also you actually can't take powers from the Paladin class even with a multiclass feat so Discipline the Unruly is out unless you take the adept power feat (don't know if you know that). Personally I would take neither of them, Discipline the Unruly requires you hitting from melee and your build would be better to stay way from enemies. Seal of Binding is a good power but it got changed so now it doesn't do any damage when you sustain it but you still take damage yourself (15 each), unless you houserule the old version in or course. if you can't do that I would suggest Life Lanterns (Divine Power) as your 25. If you havn't picked a Paragon path Miracle Worker (Divine Power) would be good, the level 12 utiliy and 20 Daily work good with your build.
For feats take a look at these:
Shared Perseverance -Divine Power- (need to be human)
Divine Cleansing -Divine Power- (need turn undead power)
Merciful Power -Divine Power- (need healer's mercy power)