I kind of like the changes though, honestly. Each of those items was giving you like 1000 mana, and there was really no reason they needed stacked. Ezreal was the one who profited most from it...but champions like Ryze and Kassadin (actually, Kassadin could literally one shot an ADC with his full-charged ult+auto with LichBane by late game, but nobody plays him since his early is too weak) could inflict some major damage with it.
with like 1800 (I think was the actual number) given between both Muramana and Seraph's, the only reason it worked so well on Ez (and why Kassadin got away with it) is because his cooldowns and mana costs were super low. Kassadin's ult costs him roughly 2/3 his mana to charge to full for his insane burst, which made him very much an all-in, do-or-die type that was soon to be oom from his ult. Ezreal doesn't have that limitation, and with just Q (Iceborn, Duskblade and both mana items) he could chunk you for close to half hp a shot...then step back into bush, reactivate duskblade, and do it again...and again...and again.
Or, just spam you to death without the DB proc. DB wasn't even essential to this, and that's how you know people overrate it instead of looking at the champs that use it.
Either way, losing all that mana and the stacking effects doesn't really harm anyone either...Kassadin and Ryze both get by with just Seraph's, RoA, and FH, and it fixes the problem with Ezreal's damage without harming his identity as the second most annoying, spammy SoB in the game (the first, of course, being the Devil of the Shrooms himself)