I hate closing threads, but luckily this was well answered so nothing more can really be gained from it staying open.
Thanks to Martyris and Zeuq for really hitting the nail on the head.
The way I like to think of it for Discipline; Shields cannot over heal. Spell Power for the win. (Once caps have been met and also considering that we don't take into account the possibility of the shield actually dropping off after 30 seconds without breaking)
Vazar, I'm glad you came to the forum to see if you were "doing it right", but we do indeed have stickied threads for a reason and it'd be nice if you had checked there first.
http://www.mmo-champion.com/threads/...iscipline-(PVE)