In my opinion this mod offers a lot of interesting mechanics with the Death Knight.

What I loved is that it has different cards that gain additional ability according to which relic you choosed to start with.

I love the idea of Rune Energy, absolutely.
Having an additional type of energy to utilize during battle.

The Invoker character is just as stated - The Defect Mark II
Aside from the interesting starting relic I don't like anything about it.
-The character art in the choosing screen is completely misleading and could have better represented itself with the same artwork of The Defect.
-It's not a different character than the defect, it has the same cards.
-Starting with 3 different orb cards makes for a mundane start in my personal opinion.
-The combination cards the starting relic creates don't offer anything too different which makes it fit right in with the game, however this relic makes the gameplay feel stuck, like I am supposed to use orbs as a main gameplay style from the get go and it takes the fun out of it for me.
One of the most enjoyable things in this game for me is building a deck based on each card I'm getting rather than the cards/relics I start with.

Now going back to the Death Knight character, it's brilliant, absolutely.
However here's a few things I think should be done to improve the character (and mod itself).
-The Death Knight has 3 relic variants that completely affects the card choices you will have along building your deck, I think getting them should not be a starting choice but random events you can bump into and perhaps even be able to collect them all.
Maybe he can have a starting relic that every time you kill a floor boss you get a choice to enhance it with either 1 of the 3 (blood, ice, evil), meaning by the 3rd floor you'll have all of them just like that.

-In my opinion the cards would be much easier to read and distinguish between Blood, Ice and Evil if it was color/symbol coded at the top of the card or even have the whole card color be different. For example cards that are affect by having Blood Symbol can be colored red, or maybe the same color but have a tiny blood symbol somewhere on it.
Reduces text, easy to read.

About the Rune energy.
I personally thought theres too many cards that spend X rune energy (with a max limit).
I think the amount should be set from the get go.
It'll give the player means to strategize better while fighting and deck building.

Lastly in my personal opinion I think there should be more cards that cost no regular energy, but do cost Rune Energy.
like a card that cost 0 energy, cost 5 rune energy, does 10 damage- The idea is to make cards that depend solely on Rune Energy, just like the drawing card that draws according to the amount of runes you have.

I think it can create a steadier flow to playing this character.

This is all.

I still haven't bumped into any of the Hearthstone inspired cards but I look forward to.

All and all this is a very interesting mod that I hope to see more of in the future.