I'm not a fan of most spell combos and don't use them much. I generally don't like surface effects. For the few I still use, In my experience for example Grease without igniting it is often better than making it a cheap damage aoe with Fire Bolt or else.
A lot maybe depends on party composition. The "combos" (kind of) I use the most are very simple, "apply prone - melee attack", "apply blind - ranged attack" or seldomly spells to get a guaranteed crit with the next attack. With Misty Step + Thunder Wave indeed Gale saved us from a wipe in some situations, but I think I hadn't used it again since I took Wyll into the party instaed of Lae'zel.
