I played my first run through the campaign with Kyra and Merisiel. Good pairing, though I did struggle a bit with damage output in the final scenario.
I played my second run through with the next 4 characters I had unlocked, chosen mostly at random at the time of unlocking: Seelah, Lini, Sagan, and Amiri. Great party. Plenty of heals, plenty of blessings, plenty of combat potential, couple of good Wisdom closers, and a couple of people who can deal with barriers and such. Ran almost the full campaign on Legendary (except for the last couple of scenarios just because I hadn't unlocked them yet.)
Recently started my third party with everyone else, because it was everyone else: Valeros, Lem, Harsk, Ezren, and Seoni. Whew this combination sucks! Combat ability is decent, but no one really closes Wisdom, no one really disables worth a damn, tiny number of blessings, essentially no heals. Swapping back to these guys as noobs from the last mob all tooled up is a serious shock to the system; I lost the very first scenario on my first attempt (on Legendary, but still...) I'm not saying that there's anything necessarily wrong with any of these guys individually, but they do _not_ feel like they work together well.
What was your worst combo in a party?