My work on Dex is largely theoretical, but given the information that you've given, it sounds off.
hit% = 5/6 + (600 - 1000) / (600 + 1000)
= 5/6 + -400/1600
That's with buffs unconsidered.
Now when you weigh in Concentration and Evasion Ascent:
hit% = 58.33(1.22) - 41.67(0.25)
= 71.16 - 10.42
If we assume that no, Evasion Ascent does not work, 71.16% sounds consistent with your results. However, I wouldn't jump to that conclusion. A few things to note:
- Luc also plays a minor role in accuracy. Aes observed a difference in hit rate (not crit rate) of up to 8% when experimenting with accuracy on build with high Luc and one with no Luc. It is really unknown exactly how Luc affects accuracy, but my preliminary tests suggested crits and non crits are calculated separately. When I tested accuracy results with varying amounts of Luc, I found that my accuracy with non crits remained consistent with my proposed accuracy formula (disregarding crits altogether, my hits vs misses were as expected). However, crits seemed to be running on a completely different and unrelated formula. The only thing that I was able to determine with certainly is that higher Luc did absolutely result in a higher frequency of hits + crits vs misses.
- If you're dealing with a smaller amount of data, it would be hard to get accurate results. When you say 70-80%, did he attack you 10 times? 100? 1000? Even 100 is not a particularly large number and there could be significant deviation from the mean, but that's probably a good start for getting somewhat accurate results. I would consider it cause for further investigation if he hit you 70-80 times out of 100, but not 7-8 out of 10.
- It would be best to test at zero bless. It is still unknown what role bless plays in accuracy/evasion, so it's best to remove it as a variable altogether.
- It is also unclear if Bash increases accuracy or not. It's certainly possibly, since it is known that a higher crit rate affects accuracy, but it is unknown whether that is a direct result of Luc or a secondary result of crit rate.
So tl;dr - maybe. I'm inclined to believe that yes, Evasion Ascent works, but it is possible that it is bugged. To say one way or the other would require quite a bit of experimenting.