Actually, that's why I love deckbuilders - because you want to find the ultimate combo and then disintegrate everything you see xD
So, some things you mentioned were intentional. For example, it was very important that the boost effect (+ power to the card) only resets when the turn ends. Because I plan to add more mechanics related to the dump (graveyard), like drawing cards from the dump or similar mechanics. And it feels reasonable not to lose the bonuses you've stacked. So your combo can become even better.
What I didn't expect is the "draw a card of a specific theme" effect drawing cards from the dump. But I kinda like it anyway. Because to make this build actually shine you need way more than just 1 card. So why not?
For example, the build where you boost the first card in hand is also quite powerful. But it also requires quite a lot of cards for a perfect build. I used to deal more than 200 dmg in a single turn.
Another example, there is a shield combos, because some cards can convert shield into damage. Quite a safe and powerful build.
So I think I won't change it now. But it's good you found it. Because doing 1 dmg using 100 cards is surelly quite boring. Need to teach the game to detect the loop somehow. Maybe the condition should be "if player played a loop "draw a card - do damage" 10 times in a row - a pop-up "your opponent gave up" appears, and you can select to continue the battle or end it straight away.
Or maybe such "cheat" builds should be boring, ahaha xD