I strongly advise you to stop at archer 2 and go rogue 2 instead.
Being a mounted class, dismounting all the time for kneeling shot will get old and tiring real fast, trust me (tried that durign reset event).
Archer 2 already brings all you really want from archer: swift step’s atribute for crit rate. Rogue 2 on the other hand makes your sneak hit buff with full uptime and brings a great filler on backstab (which just got another overheat - 3 total now- in KToS today).
By having Hackka’s skillset, rogue’s backstab and QS3 Running shot, you’l have a full kit with no real downtime against bosses. Likely the strongest archer for the upcoming World Boss patches, alongside Fletcher3 Hackka.
By the way, don’t keep yourself restricted to those +QS skill level crossbows. Enhance and transcendence work according to the clean weapon stats, so they are nowhere near as good as the practonium ones or the purple HG 315 (not to mention Lolo and Solmiki being that much stronger as well). For instance, a Purine Pevordimas Crossbow (which can go quite cheap depending on server) at +11 and Stage 4 trans is already at: 2307-2609 PATK +42 STR +29 Crit rate (a net physical attack gain of 605-637, which mind you acts mutliplicatively as well due to the log fucntion in damage formula, by experience hitting harder than the extra 60% from +2 lvls from running shot at higher levels and tougher targets)
And I really don’t see how QS3’s kit falls off later on especially on a Rogue full crit build. All the DEX you need for attacking faster nets you higher (constant due to WW cards) criticals as well. And liek I said, rotation-wise for bossing, the downtime on Running SHot is not a problem at all.