I don't want to sound cocky or something, so let me get this straight: the game is good. It's just that there are some issues with some aspect of the game that could be improved.
Also, what I say here is said thinking about FGs, not lvl 1-5 elementals.
Card related problems:
A) Lack of a way to deal with Permanents enchanted with Enchant Artefact and creatures who are Immortal (unless I missed something).
B) Too many times there's only one (or two) way(s) to deal with something.
Point A is a problem especially felt against Divine Glory (FG), where the player essentially is playing a timed match where how much time he has to kill the FG is dependent only on the number of Sundial and the kind of shields he plays and the number of Weapons the FG plays.
There's really nothing to this fight apart from luck. The only way to play this FG differently is trying to keep it from playing by destroying his lands since there's no counter for whatever he does.
For point B I'll just throw in some examples:
1) If a deck is built around some important Permanent, since many FG can destroy permanents we are forced to pick up Enchant Artifact and thus the Earth element.
2) If a deck is built around some important creature, something similar to 1 happens, and we thus have the choice to either go Time for Anubis or go Aether for Quintessence.
Essentially what I imply with point B is that if you wanna play against FGs you really feel the need to go for a rainbow deck or a fire/earth deck. With 12 elements and so many possibilities for 2 and 3 colored decks, it's a bit sad (from the metagaming point of view, aka from the "building the decks game" point of view) that so many options are viable.
If I can suggest something for point A: let Rain of Fire (or, more in general, aoe effect) affect immortal creatures. Immortal would be something more like "untargetable by something which choose a target".