and the Armenians & Scythians were basically just like playing the Parthians anyway...except with better infantry
Oh the heresy! If you've browsed around here a bit, it isn't too hard to see who my favorite faction is...

...and you should look a bit deeper into unit rosters....Armenia and Scythia both have a uniqueness that goes beyond the infantry, and either have some of the most devastating units in the game.

at this point it would probably be more fair to the AI if I turned off FoW as well, since I know the map pretty well. Though I am assuming the AI needs to "discover" territories like a player does. Also, then they would see me coming...and maybe be a bit better prepared.
For me, I learned quite a lot about game mechanics with the FoW off. And the AI is not under the influence of FoW on the campaign map, AFAIK....

I don't even know which temples are good or bad to have a governor with - I just deal with what I get.
It's a good idea to study the various temples to see what traits they pass, what ancillaries they give, and what they can do and not do for you. There's an excellent d/l guide in the Ludus Magna that will explain all the nuances better than I can.

I could probably do that short tour-of duty thing, it sort of makes sense.
Like I said, I have no proof that this helps. It's just an observation that keeps coming around....governors that do that short tour, seem to acquire less bad traits.

have you noted anything that reduces the odds of a rebel army popping up, or is it totally random and out of our hands?
There is a numerical setting that alters the frequency of rebel stacks appearing. It's been quite awhile since I've changed it...I'll have to look it up. One of the things playing without fow has shown me is just how bad random rebel stacks are for the game. Some folks like to train up-and-coming generals on them....but it really sucks for the AI. Certain areas are far more prone to getting them than others, and this can simply squelch that faction from doing anything for the whole game...or until they are wiped out. The barbarian factions get them more than others, particularly Germania, Scythia, and Britannia.

In any case, several things happen to the AI:

It's programmed to go after rebel stacks above all other considerations, even to the point of breaking off sieges, or chasing them in provinces not even their own. Worst case scenario I ever saw was the Germania faction down to its' last settlement which was under siege. Outside of town was a decent 4-star general with half a stack, and inside of town another half stack. The besieging army was quite small and could've been easily driven off. But...the AI decides that that general was better off chasing a rebel stack that was a short distance away...and so the last city falls. Pretty bad AI work, if you ask me. And to add insult to injury, that general went rebel when his last city fell, and he was killed on the very next turn by troops from the city.

Then, of course, there's the 'pound-the-hapless-peasants' routine for battle stars. I've seen the initial SPQR army general get six or seven stars for pushing a lone rebel town watch around for a number of years. And if a rebel stack gets pushed up against the edge of the board, or worse, into a corner, then the attacker will just stand there forever staring off the 'edge of the world'.

So yeah, I don't like random spawning of rebel stacks And there's another excellent discussion of this in the Ludus, btw.