Welcome to the Forum @Robert_T.This is my first post, thus I want to say cheers to all AT riders outthere.
I have a 19' ATAS and sincerely would like more power / more low end torque. I feel the low end torque is lacking and the bike starts to pull after ~4000 rpm, actually it kicks in around 5000 rpm to really feel the bike alive. One-up I would say its okaish, but 2-up + gear for camping it's not the best package. I'm not saying I can't overtake in safe conditions (quick), but I need to rev the **** out of it.
If you want to make a fast overtake you really need to go 2-3 gears down to rev the bike in that hot-spot of ~5000 rpm. I also feel the bike lacks that instant power surge if you open the throttle at it's max. It takes a bit to speed up. In my case it likes a more gradual acceleration. Might this be a sign of the tank issue plugging the fuel filter? I have never experienced any power loss or the bike stalling, just that if I open the gas at max level it doesn't fly, it takes some time to rev and then it sling shots. Quite annoying.
Have riden the bike up to 180+ km/h, thus it is fast, but I would not call it quite quick. I do believe the gearbox is too long in 2nd gear. This makes it slower for acceleration, but does make sense for the purpose of the AT, OFF-road, where you can pull that 2nd gear all around and you don't need to worry about changing gears.
All my above remarks are in comparison to my naked bike Yamaha MT07 which has an incredible engine which pulls at any **** rpm. That bike has less kg but also less HP, but it is way more quicker at accelerations and how the bike responds to opening the throttle. I would definitely love that character on my AT. Yamaha has nailed the MT07 and MT09 engines. Took MT09 for a test drive and it's a blazing engine. Would be interesting to see a Yamaha Tenere 900 built on that engine.
The AT is good at many and master of none.
As you indicated yourself, the gearbox is tall and that helps explain why the AT is rated well for offroad use. Freeway is not bad, but it does need to rev a bit higher compared to natural onroad bikes - yes. So getting full-on road performance on an offroad-capable bike will be challenging or pricey. An electric offering like from Zero comes to mind.
Maybe you won't experience the ATAS fuel tank issue. Keep an eye on it. Certainly so far many farther western countries are reporting elevated instances.