The answer to your question is "mostly" yes. Your numbers are way off, but the general mentality is solid.

Thing is, speed tunes aren't usually that simple. You can't just add 20 speed and assume it will work - and, if you do, even if it does work on UNM, it will probably stop working on NM.

You could probably start with the usual - post your roster and your current team and their stats and etc.

Even just a small increase to 3 key UNM is worth doing.

If you can manage the timing, doing 3 key unm one day and then 3 key unm & 2 key nm the next day is very much worth it

Here's my current 5. There's no real speed tune other than Brogni being 1:1 with the boss, they just bludgeon their way to enough damage. C. rate is low because fatman adds 30% and bad-el's aura boost adds 25% more. And a few people have ACC that is a little low because frankly i have too many debuffs landing so i don't need ACC as high as it should normally be.

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With all the power creep NM can definitely be bullied a bit now, but UNM mostly still needs a proper tune and gearing.  If youve got a full roster screenshot we can advise better.

Here you go :)

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At first glance, I think you'd want to just go with a 1:1 rotation using Brogni, BEK, Ninja, Ghrush, and someone like Giscard. Speeds are between 170 and 190, and you'll want Ninja to be fastest, so that he doesn't mess up turn orders with his passive - but not too fast.

Interesting... ok,  some questions. 

I would need to switch off giscards a2 to not interfere with brogni's shield,  i assume?

I currently have brogni built to do decent damage,  against unm would i need to just go ham on HP to create the biggest shield i can?

Can you elaborate on what you mean about ninja's passive? I don't see what would affect turn order in it?

And i thought unm's sped was 190, would that not be the minimum speed i need for a 1:1? Maybe im using old info?

Also,  I've just gone with stats over sets up until now,  would trying to get people into guardian or stalwart help enough to justify the work in grinding top gear in those?

Thanks as always!

Okay sry misspoke - I meant Ninja's A1, which boosts his TM. If you have your tune set up so that Ninja isn't fastest, then eventually the A1 will make him faster, which may mess things up depending on who else is around him. It may even eventually throw off the speed tune. Still - it does factor into the calc, so just plug the numbers in and you should be safe.

Yes, turn off Giscard A2, but not for the reason you're thinking - more importantly, you want the A1 for the ATK down.

UNM speed is indeed 190, but because of the way TM works, if you're between 170 and 189, you're still okay for UNM, and you can use the same tune for NM. The difference is that with those speeds, on UNM, CB gets the first turn, so you just need to adjust your delays accordingly.

Brogni doesn't need to have a huge shield - his main role is that he is blocking the speeddown and the stun with his A3. The shield is more of just a bonus.

Set bonuses are largely irrelevant - no reason to focus on things like Guardian or Stalwart.

The biggest danger with this build is when you're against blue CB, you likely won't be able to keep ATK down active. You may need to swap him out for someone else on blue CB, since ATK down is really quite important.

Also - Ghrush should have A2 and A3 off, and everyone should have WM or GS.

If Ninja will be the HP burner, could I get away with no ACC on Brogni?

chalco looks like an absolute beast

Yep.