I'm doing a similar attempt (no-loss/level 60/7 days) with a warrior and I find it faster to add droids (guard droids and 2 repair droid stacks) than attempt to solo fight the enemies with dragons. You have to go Debir-Scarlet-Bolo-Verona-Rusty-Debir initially for this though.
I had the extreme fortune of getting a bunch of call colossus scrolls (1 dug at Debir, 1 dug at Scarlet, 1 duplicate navi map at Scarlet, 1 dug at Bolo) and used one at Scarlet to get a red dragon to clear all enemies there (except for rob cuttlefish cave) and used another one at Bolo to get a black dragon.
Even with a black and red dragon, battles were either easy+long or hard+long. Filling up the 3 extra slots with the droids sped up the battles and made them a lot easier because:
1) droids draw enemy and hero attacks, and can tank big time since you just repair them
2) droids are mobile, with repair droids at movement 5 and guard droids at movement 3; very easy to keep them alive and they help pick up chests
3) droids have high phyisical and poison resistance
4) you can Sacrifice the droids to top up your other troops and just use their repair to bring back lost units; I believe you could even Sacrifice 1 repair droid stack to top up the other repair droid stack, replenishing itself whenever you get more leadership
5) the repair ability of repair droids is even more overpowered than what Eviln does for undead; it has a repair per leadership ratio of 85% to repair another stack of repair droids, 82% to repair guard droids; and this is a RELOAD ability
; this makes the 30% level 3 Eviln weak by comparison
Having fast and easy battles allowed me to reload fights until I got good chest rewards from the 3 dug chests per battle; I usually reload until I get runes/crystals/wanderer scrolls. Case in point, I have dug up 18 wanderer scrolls out of 176 chests.
I cleared Bolo of all enemies using the setup black dragon/repair droid/guard droid/repair droid/red dragon. Currently just arrived at Verona. Once I have enough mana to power Eviln I will replace the black and red dragons with bone dragons and black knights, further making the attempt for no-loss easier.
I haven't played mage, but you might want to give droids a try. Given that you have taken out the guard at the Montero bridge, you might want to reload from a save game from your Montero visit and get droids there.
EDIT: Just tried it, you can Sacrifice droids, but you can't Sacrifice other units to top them up. So the only way to have more droids is to buy more droids. This kinda sucks, I was really looking forward to a self-sustaining army. The droid-undead army would still work, but the two reserve slots would be taken up by extra repair and guard droids that you need to buy in advance.