Three Star Champions
Diana
"Number of Orbs: 3/4/5 ⇒ 3/4/6"
More orbs for Diana equals more damage. On top of the other buffs to her shield duration she already got, this could actually make scaling up Diana (and thus, Infernos) much, much better.
Zyra
"Number of Plants: 2/3/4 ⇒ 2/3/5"
Same story as Diana. More plants equals more damage, she’s getting buffs in Patch 10.5 already, and now Zyra scales better into the late game. At this point, I’m willing to bet that Inferno is actually going to be much stronger, especially late game, given how strong these scaling units will be alongside 4 and 5-star champs like Annie, Brand, and Amumu.
Rek’sai
"Spell Damage: 250/550/850 ⇒ 250/550/1000"
This will only ever matter in a Predator comp, and I guess in that scenario you would be looking to 3-star as many of those early Predators as you could. 150 extra damage is nothing to sneeze at, but this doesn’t make Rek’Sai pickable with more comps. And you’re not going to try and 3-star him unless you’re just always getting him in your shop.
Dr. Mundo
"Spell Damage: 50/100/150 ⇒ 50/100/200"
Dr. Mundo is not only a staple of the Poison comps that are so strong right now, he’s also a very strong front-line Berserker. It will be incredibly hard to get him to 3-stars, so I don’t mind his power level going up in that case.
Zed
"Clone Mana Reduction: 50/25/0 ⇒ 50/25/-125"
If you have a negative amount of mana reduction, does that mean you have a mana addition. The tl;dr is that at 3-stars you’ll be spawning Zed clones all over the place, but you don’t have to worry about that because you’re never getting a 3-star Zed.
Lux
"Spell Power: 550/900/9,999 ⇒ 550/900/99,999"
You’re never getting a 3-star Lux. A 3-star Lux could already one-shot your entire team. This buff is like adding a Death Star to a nuclear submarine.