"My point is that bots will simply invest to play in a higher rank league. They can even rent cards for more profit."
I'm pretty sure this is the best-case scenario, so It's a little comical that it was presented as a negative that "hurts the economy" even with qualifiers that it'll raise the value of cards and slow down the bots farming all the reward cards and dumping them (farming all the DEC too btw). Sure, the cheap reward cards are cool... until an actual player wants to sell one.
If bots need to rent cards then card owners get a share of all the rewards they are draining from the pool, which makes owning cards that much better instead of everyone just buying 20 spellbooks, so I don't think "hurts the economy" means what you think it means.
Also, "one account per IP" is nonsense because a lot of hardcore players run multiple accounts using cards they own, and being able to do that makes ownership even more valuable. Someone could have entire max collection and still want to buy your cards for their other accounts that need them - that is a good thing, not a bad thing. Just like bot army renting/buying is a good thing, not a bad thing. We want bots to actually participate in the economy rather than just draining rewards 24/7 with the spellbook.
P.S. captcha/verification/etc are cancer and tech-savvy bot operators could bypass them anyway. alien worlds had captcha on cloud wallets and it stopped my brother's automation of their faucet"game" for like... 1 day.
I can see how renting more cards is good for players in general, but I disagree that it is good economy that cards are artificially scarce from bots scooping them up, leaving less for real players to have available. A lot of the "big picture think" is nice in a perfect world but isn't practical in a real setting through the lense of a bot owner who thinks like a hacker. No matter how much you nerf rewards, bots WILL be there and WILL profit. It only hurts real players.
In general I personally am not a fan of multiple accounts in principle. I would prefer devs to force one account per IP. Players will be mad but it's for the better, transfer your wealth to one account quit gaming the system like a bot. (Once again artificial scarcity and hoarding is not "good economy," having more real players playing your game is.)
I agree captchas are aids. There has to be a clever and not annoying way to verify humans that hasn't been thought of yet that. Smart people assemble!