I agree HA is funny class, but the problem is, it's not working for like half of the maps. You are screwed on a town map, map with plenty hideouts for foot ranged, heavy fog (even light fog is sometimes a problem), rain (affects HA damage and horse speed/mauver), night. When i'm playing HA, i'm skipping most of these maps. But since they appears very often, I can't really enjoy the game for longer time. If i'm lucky I can play 2 or 3 maps in a row as HA. No other class is affected by map and weather so much.
Pretty much final build for HA is imo:
HA is all about shooting from horse, so there's no sense to go for PS or ATH. If you lose your horse, you are dead most of the times anyway, few more ATH or PS won't help you much here. Especially, i'm taking 3 quivers of bodkins, so I don't even have a slot for sword.
I prefer Yumi, like Elf Princess does - maybe it's not that accurate long range, but it has noticable better damage than Horn Bow. That's why I suggest 18/24 build - it gives you possibility to use Yumi. You can also go 15/27 build, but imo it's better to have slightly more damage that a bit better accuracy at this stage.
Since devs changed HA accuracy formula few months ago, HA with 174 wpf in archery and 4 HA skill has similar accuracy to ~155 wpf foot archer without HA skill. Even when you don't use a horse, your accuracy is reduced, so it's better to make two chars if you want to play strategus as archer - HA for normal servers and foot archer for strategus. Of course fastest way to exp your HA char (or any other char) is strategus
.
Anyway, on some maps, i'm having a lot of fun as HA currently.