I believe Air needs a serious buff, because right now it has a passive ability which's only effect is that it allows the creature to ignore Wings, but it also has a counter (Phase Recluse), so it's seriously unuseful and situational right now. If there were more cards that took advantage of Airbourne, Air would be much better.
I strongly believe Life should get some kind of CC/PC as well, since a mono-Life rush will be crushed by any deck with a single shield. Moreover, Life should get some new source of healing as well, since Life is about creating (-> creature generating creatures should be added) and keeping creatures alive. A passive ability like Surviving, which allows creatures to regenerate for Life quanta would be nice, and if it'd only be used for one creature I'm totally fine with that. An active or passive ability that heals the creature's owner is highly appreciated as well. The question is, does Life need spells/permanents or does Life need new creatures to add more diversity?