The Introduction of shield busting effects is a bad move
Don't get me wrong, there are definitely a few serious offenders that abuse shields to make themselves near impossible, to kill but the vast majority of champions have perfectly balanced shield mechanics. The recent patch gave certain champions such including 
the ability to outright destroy shields regardless of size or duration. This will result in said champions either being perma-banned or else invalidating more 20+ champions when they're on the rift.
Balancing Shields is easy too: reducing duration, longer cooldown, lower base values or ratios; little things that when done right make shields fulfill their role without being OP.
The main offenders the abuse shields currently are: 
(with Tahm Kench being massively nerfed as a result). The rest of the champions have either low strength "emergency shields" for blunting burst or poke, shields that have long cooldown and are down to the player to use, or shields that are weak but can be used frequently. The issue with our main offenders is as follows:
has a shield that procs when he gets low that blocks a ton of damage based on his max mana (something he'll build most the time)
has a shield that he can use that blocks a metric ton of damage and last too long (I've suggested making it scale off 20% of bonus hp with a base value, or shorten its duration)
last too long and is too strong, Nautilus is already played as a tank frequently, this shield is too much extra durability (maybe make it scale off AP for his off-meta builds)
his shield is too big and last too long, but frankly if you play the long game against him hes way more manageable because using his shield means he will likely wind up at low hp at the end of the duration. His nerfs appear to be focused on his ability to lockdown enemies, which in my opinion is the wrong change, I would simply lower the duration of his shield so it becomes a emergency defense effect.
I'd would recommend changing these "shield buster" mechanics to instead deal extra damage damage to shields, similar to what Irelia had before it was removed. If it's burst damage like Blitzcrank's ultimate, maybe %-increase to shield targets, say 20%, if its auto attack effects, the bonus shield damage should be flat value because things like attack speed and phantom hit will significantly boost its effectiveness overtime.
This one man's thoughts on the matter, What about everyone else?