i played ap karma mid a lot for a little while, and i actually like the changes a lot (almost called them a buff oops). but honestly, it's pretty much a buff. nobody cares about the damage from RW or RE. your q is on practically no cooldown lategame, so the mantra buffs reward you for spamming (and hitting) q with wayyyy more mantra'd abilities in the late game, which karma honestly really needed to scale better. before the mantra buffs, karma had an incredibly strong teamfighting presence in the mid-game, but she fell off into a support-carry role in late-game fights. the mantra buffs let her either retain her mid-game hard carry teamfighting presence by giving you more RQ's than ever, or it lets you support your team really fuckin hard by spamming RE.
like Ekko Or Feed said, it opens up options for you as a karma player. and they're really good options, and you can make choices more often for even more tactical flexibility. RQ does broken amounts of AoE damage; if you want to spam that late game, you can now. RW makes insanely good single-target peel and kite possible, as well as enables karma to do some respectable 1v1 dueling. RE is just a flat out broken teamfighting tool; you don't use it when you're in the middle of the enemy team, you use it when you're in the middle of YOUR team so you get a free Locket + Talisman. the way they changed RE's ally shield value means it scales better into late game, too.
tldr the karma changes give her massive late-game presence without taking much away from any of her other phases or capabilities. solid buff all around.