Frustration with Spellforce combat

[David Lamb]

I hope real-time strategy fits this group.

I bought a copy of Spellforce Platinum (from the early 2000's) from
gamestop a few months ago, and started playing it recently. I got as far
as the Leafhade campaign before I started getting nearly-wiped-out in
mass combat, so resorted to a walkthrough at
http://www.gamefaqs.com/pc/561649-spellforce-the-order-of-dawn/faqs/30125

That helped a lot with troop composition, but I still took more losses
than seemed reasonable. Clerics would attack enemies instead of hanging
back and healing. Marksmen would move in closer than tanks (initially
recruits, later armsmen) and get hurt or killed. Clerics would take
forever to get off their butts and heal anybody.

Trying to keep order in the ranks seems to be proving impossible. The
best I can do is select the whole mob, select the picture of the group
of tanks, move them forward a little bit, select the marksmen, move them
behind the tanks, select the clerics, move them behind the marksmen, and
have the whole thing fall apart when the army engages in combat.

I'm not ready to give up yet, but I have two questions:

Immediate: is there something missing in the way I'm trying to manage my
army?

Longer term: are there more recent RTS where your army isn't outright
stupid?