Zeke's Herald is problematic in that the stats it gives on its own aren't enough to justify buying it. Supports can't make good use of the AD or the lifesteal and the CDR often goes to waste due to the high amount of CDR support items. Other roles have far better appealing items that they can buy. The item is a waste of a slot on the champions that could make good use of the aura and completely terrible on any champion that isn't AD. It's bad on supports because the stats and build path are terrible. It's bad on damage dealers because it doesn't give that much damage. For a support it'd be like if your Irelia top built Abyssal so that your all magic damage team could do more damage.
The only time Zeke's is worth buying is if you have 3+ physical damage dealers on your team who would heavily benefit from it. Even then, though, it's usually still not worth building over other items. It's a weird situation where the only time the item is really effective is when the other four members of your team are all AD. The problem with this is that your team will all be dealing the same type of damage, so the enemy team will just itemize accordingly and hard counter your team. Making full use of Zeke's usually means you have a terrible teamcomp.
Neither the aura nor the stats have leeway to be buffed. The item is already gold efficient on its own. If you nerf the stats to buff the aura, you only further drive it into its niche. If you nerf the aura to buff the stats, then there really becomes no reason to take it over other items that give the same stats with better utility. If you just buff it, then everybody will start taking it because of its gold efficiency. It could be made better for supports by switching some of the cooldown reduction to more health, but this doesn't change any of its core problems.
The new Zeke's is a far better step in the right direction for multiple reasons.
First: It still retains the "damage boost" that the previous aura gave albeit as a charging method instead of a constant aura. It only loses out on the lifesteal.
Second: Because it's a charging method instead of a constant aura, it has room for counterplay. You can engage when the charges are low and disengage when the charges are high to avoid the damage boost. It also partially negates the "invisible power" provided by the aura (hopefully there will be a visual indicator for the passive).
Third: The item's stats make it a good pickup for multiple roles. Mages, supports, and tanks could make good use of the mixed stats it provides.
Fourth: It has a better build path. This goes hand in hand with reason #3.
Fifth: The passive is useful on pretty much every role. Tanks and supports could use it to boost the damage of a team member. Every other role would like the extra crit/ap.
In fact, I'd guess that the new item is a little bit too strong. It gives a ridiculous amount of stats for only 2300 gold, and the passive looks monstrous. I guess it'd all depend on how fast the charges accumulate and what the stats for the item are when it actually goes live though.