After playing Horizon Walker in heroics for a couple of days now I've noticed a couple of issues that need polishing in order to make this tree feel better. Please note, I don't think these changes will make the tree noticeably more powerful or actually perform better in most circumstances, but they will definitely improve the feel of the tree.
1) No Missed Step (the Dex trance) has an appallingly low recharge rate, which translates into far lower uptime than other trances. I understand you were going for a mechanic that allowed characters without SP bars to still use the trance, but please increase the recharge rate on this. It needs to go to either a) on vorpal regains a charge, or b) chance on crit to regain a charge. As it is now, it just feels "sparse" or "stingy". I constantly felt like I was low on charges, and in fact frequently ran out for several minutes before gaining another charge. Many times I would see vorpal after vorpal fail to recharge it, and it just ended up feeling like a chore to monitor charges and make sure I only used them at key moments - that definitely doesn't feel good or fun. Of course resources need management, but this just felt like drudgery.
2) Corner the Quarry is kind of a weird ability. Many times it seems to fail to activate even when inspecting the mob reveals it's active on them. There is also no visible indicator for if it succeeds or not. It's able to be used every 6 seconds, but says it has a 20 second cooldown in the tooltip - is that 20 sec between actually making things immobile? I don't know exactly what to do with this one, but it needs some polish.
3) Speaking of feeling "sparse," the 12 second uptime on the Misty Step ranged power boost, and the 12 second uptime on the displacement boost also felt a tad too short and like a bit of a management "chore" - something like extending the buff to 15 seconds would be a small change but go a long way toward lessening the "ability management overload" feeling. I'm all for an active playstyle - I've mostly played casters during my 11 years on DDO, and those are the epitome of an active playstyle - but the number of things to manage with Horizon Walker and the short intervals make it feel overly busy.
Bonus Suggestion:
I totally understand why Improved Precise Shot was nerfed back when Inquisitive and throwers were massively overpowered, but we're several nerfs down the line now, and single target ranged DPS (i.e. due to archer's focus) soooo massively overshadows IPS that it's a bit comical now. With the changes to doubleshot, the nerfs to several ranged styles, and the major buffs to single-target ranged dps, I think it's time to take off the -20% to damage that IPS imposes. It's so lopsided at this point that I considered not even taking IPS this life, especially with the way Horizon Walker incentivizes single target focus. I ultimately did take it, since there are some moments when swapping stances still makes sense, but I use it rarely. I don't think a key ranged ability should be so marginalized. Also, it's another one of those things that "feels bad" or seems "stingy" when playing ranged, and it's always in the back of my mind when I have IPS on that I'm gimping myself. Please roll back that particular nerf.