First of all, thanks for taking the time to leave two different comments!
Card making is a core aspect of what I think can separate the game and make it different enough from other similar titles, so I wanna tread carefully about tweaking the mechanic.
The original way it worked (and the way it still works for "Adventure mode" is basically what you are suggesting, every ability comes in a gem, including trigger times, and atk/res. The reason I enabled every ability to be usable in the roguelike mode is to give the users more of an idea of what can be done with the mechanic. In the future the entire system will be remade for it to be less clunky since selecting each thing from a small dropdown list clearly isn't very appealing or intuitive. Upcoming versions will likely include some sort of variation on the forge not only visually but also giving you access to a small pool of randomized effects you can use as to not overwhelm the player with 50 effects at once.
Separation of effects by card color/type is already a feature (which is similar to what you suggested) but it is toggled off at the moment (Altho still toggleable in Adventure mode) because there aren't enough effects for every of the 6 colors to have enough variety. More effects will be coming in the future and once those are added I might allow the segregation of effects by color again but adding effects means having to teach the AI how to use them effectively and since that's very time consuming, this will come later down the road.
Regarding more keywords being implemented, you bet they will be very soon. The only reason keywords for entering the battlefield of milling aren't there is because I literally made the entire mechanic from the ground up 8 hours before posting the demo. I wanted to make an early post but realized not having keywords at all was going to be a point of severe scrutiny, so I did what I could. I'm surprised it turned out as well as it did considering it didn't exist at all the morning the Demoday started. Also fyi pierce already exists as a mechanic exactly as you described it.
Your idea of the relics is interesting but I think it might be a bit too far from the concept I have in mind and reworking things to fit such system would be too costly timewise.
A different relic/equipment system is being worked on however. These pieces of equipment will offer benefits to facilitate or encourage certain playstyles such as making your burn spells deal extra damage if you control no minions, or giving you extra mana at the start of the combat at the cost of losing access to your graveyard.
Regarding balance, I understand your skepticism. But the philosophy that I had in mind when first designing the current system is that there is fun to be had making overpowered, over the top cards that can only be kept in check by other cards that are also powerful. I understand however that this is very dangerous since it might lead to players reaching higher floors unprepared and losing in a frustrating fashion against a strong enemy. Balance is very much a work in progress so I'll be tweaking it as I continue to dev.
I'm not sure I agree with the luck events being a bad thing to have since I feel they give a nice break to the time consuming and more brain taxing combat. I've heard feedback asking for even less combat and more alternatives to moving up the castle, for example. Either way, I'll keep your opinion in mind.
Lastly, the wizard ability gets better once you upgrade it in the menu since you can skip combat while also getting loot from the floor.
That was a long post, but thanks again for your comments and your time!