I really doubt Dimaria can replicate all the damage Laxus took in his life with just one spell. Just because Age Scratch worked that well on Wendy doesn't mean it'll be as effective on Laxus. Like any other spell in the series, Age Scratch has it's limits. Freed (a nasty Hax user himself) said "Nothing is perfect in this world" when Evergreen mentioned his Jutsu Shiki is "Perfect".
Can Dimaria hurt Acno with Age Scratch as well? The same Acno who laughed off anything Irene (who's much stronger than Dimaria) threw at him in his Base form? She probably can't even replicate the damage a half-dead Igneel's roar did to him, let alone all the damage he took in his life lol.
Laxus is no Acno, but claiming Dimaria can replicate all the damage Laxus took in his life (including multiple
serious spells from Assault Wahl) with just one casual spell, even if it's just mental damage, is speculation at best and a bit ridiculous if you ask me. That's like claiming Seilah can control Gildarts because she could control Elfman or that Makarov's Fairy Law will one-shot Mard because it one-shotted Jose.
Dimaria's feats with Age Scratch are not all that impressive, anyway. Wendy took 2 of those and could still fight. Even if Dimaria does manage to get Laxus with it (there's no guarantee she would), a single Age Scratch,
at best, should do as much damage to Laxus as one of Assault Wahl's spells would. Nothing a healthy Laxus can't take.
Her Lasers should be easily dodgeable for a healthy Laxus. The guy
blitzed Assault Wahl after
zigzaging through his bullets, while being injured (from attacks Wahl managed to land as easily as he did due to the MBP messing Laxus up) and hindered by MBP putting a constant strain on his body and limiting both his physical and magical abilities. Not to mention he dodged the first few
without Lightning Body.
TO Chelia outsped and deflected one of her lasers
without using her God Slayer Magic. She reacted and defended against her "Full power attack" from point blank range. Laxus should be able to do the same, if not better.
The way I see it, Laxus is at a level above the Spriggans and below Irene and August. One casual nuke from him was portrayed to potentially one-shot (or at least severely injure) Azir and with one of his strongest attacks, Red Lightning, he went right through Assault Wahl. Replace Laxus with God Soul Dimaria in all the fights he took part in this arc, nerf her with MBP, put her up against Wahl and give him immunity to her Magic for a few minutes. Do you see her performing as good as Laxus did? Do you see Dimaria casually severely damaging/KO'ing Azir with one spell? A fellow Spriggan? I don't.
Laxus is out of her league. A Low-Mid diff win for him imo. Possibly even easier than that. He should be able to tank/dodge anything she throws at him. Assuming she manages to get her spells off before getting blitzed/nuked.