Yes but you can't afford horses (resource-wise).
And they're really hard to keep grouped with infantry, they're much better with the other horse archers who are also ranged, and also mounted with the same speed.
Fanatacism can surely help with the morale a bit, but Voi will still take tremendous losses against just about anything, including LA indies. I mean, I don't even buy that quality of troops for expansion in EA anymore, the attrition is just too costly and cumbersome.
I mean it's great if the PoD is taking a province a turn - if he can consistently find provinces that he can take. However, with Sloth3 and a Voi army, you're going to have a really tough time keeping up with expansion using your troops. It takes a couple of extra turns to rev up a solid force of horse archers, but they can take most indies with very few losses once they hit critical mass, so you are building up the next force, rather than running on a "Voi reinforcement" treadmill.
To look at it another way, if your PoD takes 10 (starts in month 2, and you wait until turn 2 to attack) provinces in the first year, and your army takes 6 provinces, then you aren't much better off than the player whose main army takes 9 provinces in that first year, and then sends another force out 3 turns later which takes 6 as well. Also if he's affording a decent squad of troops every 3 turns, and is positioned well, he might even be beating your expansion rate with the PoD - but we won't go there because you could suppose that your 8 prot, 8 morale Voi didn't die in droves.
My point is just that more often than not, no matter which direction you take it, Bogarus' expansion will tend to be mediocre. But it'll be mediocre with their best troops alone, or with an awake SC and a steaming pile of Voi.