Cu Alter Bond CE worth it?

That's really a hard question to answer. The guts he gets from that ce is pretty good (about 2.5k at max HP) and it also helps plays to his strengths as being a berserker with good staying power (similar to his lancer counter part) which is something that makes Herc so good.

But of course you are right as well he loses alot of dmg potential from it being a 4 star ce with only 100 atk added with a low modifier to NP dmg. It is a really hard call to be honest. I think I personally would slightly prefer bond CE to black grail, but I would still use one with a black grail or golden sumo on.

At the end of the day though, I think there are quite a few people who will just use their own setup with either opting for lunchtime or mona lisa ces.

It is good if you have him NP>2, in a solo game. But generally you can have other CE to put him in a team.

i am close to it to (and my cu is 100 10/10/10 to) but i dont think i will ever put his ce on him unless i am going for solo some boss.
The true strenght of Cu alter is his team play.
Someone compared him to Hercules, and they are similar in some aspect, but Cu is a much better team fighter.
Stacking defence up and attack down is extreamly powerfull.
Just think about it, mash np+mash 1+ waver 2+cu 1 is 80% def up and 20% attack down for 3 turn. And you still have the second hightest attack in the game to do ton of damage.

Personally i think is better to go for his playstyle and increasing his buster.

It's great if you're using him as a last stand or solo servant. Otherwise you're better off with a buster up CE.

I'd much rather see a buster up CE like Limited Zero/Over or Hero Elly. Ups his buster card strength while still adding some juice to his NP. Cu Alter charges his NP way too slowly for my tastes.

That bond CE will be very helpful to people during Nerofest, however. When it comes to support, sometimes it's best to just have the option out there. For example, I put my Nightingale instead of Vlad on my support despite the fact she's pretty unpopular. But at least it offers the option to people.