From how it sounded to me:
1. Invokers can use quasi-elemental magic, which is a step higher than paraelemental, while only ice and ooze are in the paraelemental paths that an invoker can learn.
2. Add magma and smoke, so that Invokers have more paths to choose from but not enough points to toss five into everything, so that invokers have more options for variety, like "I wonder if that invoker can use a fireshield or a magma shield...hrmmmm." Leaves the other guy guessing until they actually fight.

Anyway, that's basically how I read it *shrugs*