Remathilis
Legend
While arguably a PC's advantage in said system is the ability to one shot their enemies, I find that a rather thin one as well. I find one shoting a major encounter to be anticlimactic; it might be cool in the moment, but one shot mechanics (be it wp crits, save or die, or similar) rarely lead to satisfying results.Worth noting perhaps that this particular example of randomness only has negative outcomes; meaning that indeed if the PCs are more often affected the net result will be a negative for them.
But not all randomness has to result in a net negative. I have a wild magic surge table that has results beneficial, baneful, and neutral, mostly fairly minor but some go to extremes in all directions...and the players just love magic surges!
Same goes for the Deck of Many Things - the results aren't all negative, the players love them, and I-as-DM am happy to chuck one out there now and then...which might explain why Deck-generated keeps have been sprouting like mushrooms across my setting: I can shuffle the cards until the colour wears off and sure as shootin' somebody's still gonna pull that damn Keep card!
The net-negative randomness of fumbles is IMO balanced off by the net-positive randomness of criticals.
Star Wars d20 was on to a really good idea with its VP-WP hit point system. They just didn't use it right, and allowed for too many means of bypassing VP.
I feel a similar way about fumbles. D&D has never had a proper fumble mechanic, and most DM-made ones end up unduly harsh. The trade off for weapon breakage, slip and falls, and other things like that is potentially double damage crits. And if the crit system allows more than that (like grievous wounds, loss of limbs or death) your back to the wound problem above.