Please Revert Health Regen (and Mana Regen) Changes
I don't know why this was done in the first place, but it's just about the only statistic that improves moreso based on the champion you play (Attack Speed being the other, I believe). Ruby Crystal improves Health by 150, no matter who you are. Long Sword gives +10 damage regardless of who you are as well. However, Rejuv Bead gives 1.5 HP/5 to level 1 Gnar/Soraka, but 20 HP/5 to level 18 Heimerdinger (and, btw, please put him in line with other champions, at least).
So, why is this a bad mechanic? Because low HP Regen (and MP Regen) values are used by Riot to balance a champion's lane viability. You want to nerf someone's lane sustain, you tank one of those two. But, if that champion can't even make that up with more regen, it drains the viability of the stat as a whole. Right now, Health Regen is a useless item buy because level 6 Regen is just plain terrible save Rejuv Beads, and generally isn't worth it on larger items until level 18, at which point the game's max Regen items (at 100% Max Regen) barely hit the values they once were pre-fix (maxed at 20 HP/5).
The stat is downright useless at low levels, and only climbs to its old viability on a handful of champions. It makes Rejuv Beads an obscenely good buy on some of the game's best rejuvenators, but then the upgrades only double the improvement for 20x the cost in some cases? The max (non-Warmog's) used to quadruple a Rejuvenation Bead, meanwhile. Same arguments go for MP, as well. Casters are better off grabbing what they need in runes/masteries pre-6, grab a few Mana Faerie Charms (and maybe Morellonomicon/Forbidden Idol), and hardly worry about mana again, while low-MP-Regen champs generally have to go the Mana route, but hardly mind it because Mana Regen is not capable of being a full-fledged strategy but by a handful of champions.
Final note, if you are going to make an item mechanic that basically immitates scaling runes, its ratio should also scale similarly. If you change HP Regen from 5 per 5 to generally 3 + .2-.3 per level, it's going to suck early game. There should be an endgame boost to it to make the sacrifice actually worthwhile instead of ending up dead-even. But really, an item that gets better by the level shouldn't exist.