This is entirely irrelevant, if it wasn't forbade by the combatants it is allowed. Given that Garrosh himself didn't consider it cheating when Thrall used magic in their first duel, I'm gonna go with that means it wasn't cheating, otherwise he would have used against Thrall to win the duel by default, but he didn't care, nor did any of the presumably hundreds of witnesses.
So, not cheating.
Nowhere in the lore is it stated that armor and more than 1 weapon is not allowed in Mak'gora (in fact, in every instance where these were rules in a duel they had to specifically be declared before the fight, which wouldn't need to be done if they were baseline rules), it is also not said anywhere that magic is considered a "weapon"... And even if that were true, which it's not, it would mean that both Garrosh and Thrall cheated in their first duel, because Garrosh was duel wielding and they both wore armor, which would mean neither of them care for the (nonexistant) traditional rules and therefore it wasn't cheating in either case in either fight.but the rules says one weapon and no armor, thrall had armor and used 2 "weapons"
even if he cheated, forgiveness can be archived.