Pretty good but I'd fix a few things for next time
1. Some of the cards don't make sense as to which category they are in such as Hydra being in earth and not water. Minor though.
2. Some of the four elements are too weak or strong in comparison. Earth is overpowered compared to other elements. While fire was easy to get points for, there didn't seem like all that much to spend it on unless you went chronomancer and used those extra points to cast spells in your extra turns. Water is underpowered with not a single really good monster combat wise and was the hardest to get points for. Air seems a bit limited as well.
3. I found that certain sub-elements (for lack of a better term) such as ice cards under water and lightning cards under air (both of which could be elements in themselves) were not numerous enough. I don't mind molding everything except the specialist column to just 4 elements, but I need more within that. This is especially true with ice as I can only recall two monsters and zero spells. At least lightning had a wall, possibly a titan (I couldn't tell if that was lightning or not), and a few spells. It's cool to add those in there, we just need a larger selection of them to choose from.
4. It's great how each class has different strengths and weaknesses, but the classes aren't balanced enough. Some like mad hermit and beast master were crazy good. Some like chaotic and dominater were underpowered compared to the rest. Sorcery was good but didn't have a single creature and was therefore literally all spells. By far the most overpowering was chronomancer though. Summon a chrono engine and you will most likely win. Summon two and it's practically a guarantee and they only cost 7. It'd be no fun if you nerfed the classes (especially my chrono XD), so my advice is to just bring them all up to the same level. You also may want to add a few classes, although it's hardly needed as there is already plenty of choices and variation.
5. You need a bigger selection of cards. And when adding to that selection, I would do in a way that keeps points 1-4 that I made in mind.
6. This point isn't needed, I just though it might be cool to add a separate place for spells, rather then mixing them in with monsters. That way we could have four monsters per column and a couple or even a few spells as well. Keep in mind that when adding a bigger selection, there may need to be more room for players to choose a bit more to take with them into the duel.
This is a good game, and has the potential to become something really great as it is already one of the better card games have played online. This isn't my game, so in the end it's up to you what to do with it. But I hope you take at least most of my advice. I give you 4/5 and 7 out of ten, because it's better than a 6, but just not quite an 8 in my view. Keep in mind that I'm a harsh grader who doesn't put tens on everything I kind of like or better so a 7 is really good from me.