A3 shines or dies depending on your selection of later ranks, and of course besides how you can effectively use the class.
The usual reasons for going A3:
Max Swiftstep: works better for builds with a decent amount of DEX. Low DEX = low crit rate and evasion bonuses. Max Moving Shot Movement Speed is great for using no-cast no-aftercast-delay/animation spammable skills (e.g. crit shot, split arrow, etc.) and AA-ing. Not worth maxing for low DEX, high STR builds.
Max Multi shot: highest damaging skill per cast in the Archer tree with decent scaling - and the reason why you can’t move while casting it, it’s a bit tricky to land and gets cancelled when you’re attacked. The issue with quick charging not working at all times is due to server lag, not the skill or anything buggy. Not worth if you go Fletcher3 or AA (auto-attack build). Won’t get obsolete for skill-based builds.
Max Kneeling Shot: Don’t mind the damage bonus from DEX. Range and ASPD bonus is what makes this skill great albeit situational in usage. 10% bonus crit rate helps if you have a good amount of DEX (similar to Swiftstep’s crit rate attribute). Bad for PVP/GvG though. Maxing it works best for AA builds (e.g. works with QS’ running shot). Won’t get obsolete for AA builds.
Max Twin Arrows: no-cast no-aftercast-delay/animation skill with just 7sec cooldown. You can move around (w/ Swiftstep’s moving shot movespeed bonus) while spamming the overheat charges. Decent damage, and consecutively consuming all five charges totals similarly to a semi-burst high damaging skill. Can work as filler for other skills at later ranks. Won’t get obsolete and can work for either skill-based (as filler) or AA builds (as burst).
Max Heavy Shot (?): Rarely maxed. Not really sure about maxing it (might be useful for PVP). Can take it at just level 1 as knockback filler while Full Draw is on CD. I’ve read somewhere it has a hidden mechanic making it deal 50% more damage against plate-wearing targets so maybe maxing it does make sense if it fits your build.
As @Dream said, the problem with the build is just that it lacks AOE (at these levels) and that’s where A2 R1 is better.
Other than that, it’s NOT “completely garbage” unless your whole r1 to r7 build is.