Well, considering that technically, Shielder/1h cav will be your main focus, I'd start by getting either 15 str or at least enough str for your items, get your PS up, and then get 3-4 riding asap. The bow probably won't even make an appearance (despite the investment) until later. See, the thing I've realized about this build, and any build like it is this..... It'll be a BITCH to level up. If I were to respec right now (from lvl 29 or 30), I'd still only be lvl 24-27, and using the calculator, I can only be extremely mediocre, if sub-par at best. Like most builds, it shines at lvl 30.
Also, I know I shouldn't base builds on/include Heirlooms, but I'm just saying that the build might possibly work for me because Heirlooms give you quite a bit of leeway when it comes to stats and wpf.
-edit: If I were to Respec into this build right now, I'd be right about here:
Level 27 (2 359 534 xp)
* Strength: 15
* Agility: 18
* Skills to attributes: 2
* Power Strike: 5
* Shield: 4
* Athletics: 2
* Riding: 4
* Power Draw: 5
* Weapon Master: 6
* One Handed: 90
* Archery: 136
While that's not terrible, and it's doable, I'm still missing 9 skill points that are pretty necessary. I won't have the 3 HA, I won't have 6 athletics, and I won't have 6 riding. None of those are really essential to pulling this off, and I could just avoid firing from horse back, and I hate being slow (low athletics), but I'll have a horse, so, Y'know.