Baal on hard mode as a mage

[Annex]

Level 55 mage, hard mode, on last boss (Baal). Just cant get him down (killed him on Normal mode no problem). Previous bosses were cake on hard. He however just destroys me. Tried many combinations of units and the best I can do is get him down to 25%. Few things that happen:

- He does his sword thing at the start, which I can generally avoid throughout most of the fight but at the start it hurts quite a bit
- He uses the sword thing whenever he summons units as I cannot reach him fast enough to prevent him from doing so
- He will sometimes summon twice in a row, creating a vast barrier between myself and him
- My front line units are Paladins and Knights. I keep Stone Skin on them at all times. I use haste level 3 to get them to the boss in the first round
- Have five wanderer spells going including attack, defense, intellect, crit and 20% leadership stack
- Been casting Magic Spring on one or two units to keep my mana pool sustained
- Been casting resurrection to bring back fallen units
- Been using Archmages for their shield buff
- My remaining two units (in my last attempt) have been Cyclops for ranged attack and Bone Dragons or Black Knights to be used as a double stack to try to convince the boss to attack the knight/paladin instead of using his flying sword

Now, few observations. I cannot use any non-retaliation units as they get annihilated in the first turn by the flying sword. I bring in 500 royal snakes and I lose 400 in the opening volley. Bill Gilberts forces get annihilated quickly, and his ranged units are too fricking stupid to move when the ground collapses so losing those two ranged units hurts.

Any advice?