There go my days of enjoying the ultimate green weapon. It was fun while it lasted. 

Also, OPs recommendation is whack. why will you ultimate if you cannot use the ultimate part of the ultimate LOL

It's not a bad thing but what is the purpose of Kutum if you can just use AP offhand that gives you 10% more damage to back attack and crit while also hitting AP cap? Kutum is like 3.5x more expensive to caphras and it doesn't even do better for end game PvE. Nouver also kinda pointless at end game PvP because you can just use AP offhand that gives 10% to special attack which is way better than pushing the irrelevant AP brackets. Only thing boss offhands have over the AP one is defensive stats which are lackluster in this meta where everyone does so much damage.

Build, Some people will prefer 10% Special attack evasion, while other 10% Special attack damage. de facto the 2 cancel each other out.

For pve.  The PVE cap is the stupidity. Any cap in any shape and form is pure lazyness and trouble making.

What is there to build when one is clearly better than the other for both content? They also do not cancel each other out 1:1. Special attack damage is stronger sicne you can get more of it while special attack evasion is hard to get with 30% being normal and 48% if you use lighstones and buffs which generally only DP builds use. So for most people, its 30 to 33%.

You also don't need that stat for PvE, AP offhand is the best as long as you can hit AP cap and that is very possible even for end game spots. PvE cap exists so people can't just go to a mid to mid-high tier spot and kill the mobs super easily. They need to exist for some spots to prevent people from killing to quickly and affecting the economy. At high end spots its a different story. 

This is the same problem we had with green helmets being the best for end game and green awakening weapon being the best for end game when playing succession. Higher grade item should be outright better, not a side-grade or alternative.

This is not true, that's not how they work.

Also special evasion get explonentially stronger the more you have, while extra attack damage (and similar) is the opposite, the more you have the less value one more point have.

In PvP classes that can build tanky are actually better with a boss offhand, since ppl onecombo each other even at low AP anyways, the extra special attack damage is not required. These are only better on glasscanon classes, on classes where defense don't matter anyway.

The issues is that you can exploit caps with these items, which kinda ruins the point of caps, and it's not like bdo would need more damage either.

If you drop an ap bracket, even if it is the 316 bracket, 323, 330 or whatever else then Nouver is is better for Damage as long as the enemy isn't CCed. Most people are overvaluing Critical Hit damage. In high end PvP when people are running 35% special evasion 10% critical hit damage is less than 3% damage on a 100% critical hit chance skill. Combo damage increases quite a bit though. But you lose 10% special evasion when running a green offhand which increases the damage you receive by a lot more than the damage you gain. 10% resistances is also a stat which shouldn't be forgotten. 

You can make the following arguement: for green offhands 10% special attack damage is worth a crystal slot. 

The difference in ap between nouver and ap offhand when losing an ap bracket is worth a crystal slot too.

The 10% special evasion is worth a crystal slot.

The 10% resists is worth a crystal slot.

So now you're 3 crystal slots for 1 in PvP. Yes your damage can be higher with green offhand if you don't lose an ap bracket but as soon as you are using skills without 100% critical hit rate that benefit is also starting to get questionable.

So now the only benefit left is the price difference 30b vs 100b. I can't deny green offhands start to look really appealing in that regard. There often is quite a high price difference between BIS items and which are good though. 

And regarding PvE: In some certain spots ap offhand might be better but I'm confident in the vast majority of spots kutum/blackstar offhand will still be better. 

AP cap doesn't mean it's a hardcap. Recently I read some info (not sure if true) that Olun for example has a 70% AP cap. After hitting the AP cap each AP is worth 0.7 AP before hitting softcap. There were also some 5% softcap spots at which Ap offhand would maybe be better.

Yeah it's around 3-3.6% increase on non cc targets, however the AP you lose is even worse increase, and that is the main problem. Going above 309 is pointless. I'm at 336 and the difference compared to 309 is hardly visible.

Wait people are actually complaining about this? I don't get it, i think they should buff the ap offhand further, who the hell wants to swap between kutum and nouver, nothing annoys me more than having to swap those items when someone asks for a DFS, the things are cheap anyway(people don't c20 their kutum before everything else), it's not like you get a massive deal on the price of the greens. Some people are just salty for no reason, and anti fun, or some sore loser with a pen bs offhand.

And how can some people say it's easy to hit hexe ap cap? Are you serious? that's like 330+ AP with a perfume and standard buffs to reach it. OMG someone who can afford a special pve set with pen distos and maybe some pen deboreka is pulling 3% more trash at hexe OMG it's breaking the game, oh no someone that has all the gear in game can get a bit more silver per hour, oh no.

So yea, let the poor people grinding 5% more trash at Jade with the green hand alone and go touch some grass.

3B vs 9B +(for green vs boss) value wise add in caphras green needs 9615(28.9B) and boss off hands need 29,403 caphras(88.2B) , also its more than 3% increase in trash loot , 3% of 600m+ is  still a extra 180m  a hour. You need to touch grass with a attitude like that. A item worth quarter of a value of another item should not be out performing it not to the extent it is right now.

Edit: NA kutum is 9.8B where as green grade @ pen is 3.7B

*18m not 180m