Yeah these Spec Ops weren't geniuses.
The way I play with Archer is, I put all of my civs into Mana early on and upgrade Zerg Air damage. Once my team mates sim I upgrade hydra damage and armor and get comfortable exping until I hit L3. Then I'll either start boosting my health depending on who I'm fighting or continue pumping Mana.
Now, it's of course difficult to go into how to use them. Because it's different game to game. The way I see a lot of people use them is fairly silly. They travel with them in packs with their archer and someone feeds on them. It's not a great idea to do this. With you're L3 up the best thing to do is to destroy some defenses or sims, or go capture bases.
Most of the time I find it's best to do this as an enemy is on recovery and slowly burn them down. Once I hit L4 I just use it whenever I feel like I've got a shot at killing them and continue using L3 to block recovery or destroy their bases.
The idea is similar to using HP Spec Ops. You add in more and more pressure and keep yourself just out of their kill range. There is of course a counter, such as Summoner. Plague and ling packs completely destroy these and make it particularly difficult to maintain exp gain and pressure. Mut, as well is no picnic.
As you mentioned, I'm obviously discussing Archer, Warrior and Mut as in their spells. Mut and Warrior of course have great base damage. Archer is ranged though and has a decent damage against defenses. Not so much other players of course, excluding Mech and Volt.
None.