Hi there...
Lord Aranthus is my fave without a shadow of a doubt. It's most satisfying winning when the other team just tears themselves to shreds with him just sitting there. Combined with a healer he's most useful, and cheap (relatively) to max out.
I'd go for the highland archer out of those cards believe it or not... 3 mana for 2 damage is quite useful, and I'm looking to take that one up to L9, yr L6 will bring me about a third of the way there!
Cheers.
@steevc and @slobberchops will want to get in on this I am sure!
I love the lord too! Today I've managed to get my first one of those maxed (it's actually the first one ever I've maxed out I think lol)
Good luck!