illustrious GM, I introduced the same mechanic into my 2e game. I thought it would be a fun way of keeping things interesting, so the characters didn't spend their first several levels refining the finer points of kobold combat. In their first outing with the d30 at their backs, they even managed to take down a mind flayer. By the skin of their teeth, granted, but it definitely levelled the playing field enough that it was possible.Having been inducted into the Order of the d30 by my
Suffice it to say that, with the head of a mind flayer swinging from their collective belt, they went into the next session with a bit of swagger. The gauntlet was thrown, and having giveth, it was time to taketh away. That night, the party learned a valuable lesson - the d30 is of great use when fighting a singular big bad, when fighting swarms of small timers, not so much. Challenged by a Hobgoblin and his Goblin minions, a toll was demanded in order to cross a bridge. The party declined, and combat was joined. Suffice it to say that the Goblins cleaned their clocks. None of the party had any area of effect spells, and so it was 7 goblins and a Hobgoblin against 6 low level characters. There were lots of swings, lots of misses, but when they hit, the Goblins did just as much damage as the PCs, and the PCs didn't out-HP the Goblins by that much, so the hits, few and far between as they were, wreaked devastating havoc upon both sides. The d30 was effectively neutralized since if it was used on an attack roll, it only took down one goblin. If it was used for damage, it didn't matter whether the hit did 6 points of damage or 26.
In the end, it was the quick thinking of the rogue that saved the party. With the rest of the party unconscious and faced with two Goblins, he chose to parley. Seeing their leader down and the other five Goblins in a similar state, they agreed. The party lost half of the gold they took from the corpse of the mindflayer, but they lived.
They seem to have learned the lesson, a bit. Last night, when confronted by nine dwarves - six unarmed, two with daggers, and one with an axe - they chose to go for the reaction roll and talk their way out of combat, rather than rush in headlong.
I call that growth.