I played a Trapsin in Diablo II. It was a fun class that turned the game into action tower defense. Drop traps, throw my pitiful attacks at the enemy, and kite them around traps until they fell down. I was particularly fond of the the exploding corpse trap and the cow level. Explosion damage scaled based on the enemy’s hit points, and cows were big tanks. Killing the first one took a while, then they fell like dominoes as high-damage corpses converted cows into more high-damage corpses.
This scaled nicely based on enemy hit points but not on group size. Enemy hit points scaled up with group size, but the trap’s damage was scaled on the enemy’s base hit points, not its scaled hit points. That is, the trap that was devastating on a solo map did less and less as the team size grew, because enemy hit points increased but trap damage did not. (Granted, neither did any other damage source, but there is a large difference between falling dominoes that take out a whole group and “kite, 1 dies and damages several, kite more, 1 dies and damages several, kite more…”)
With no allies, I could solo the map easily by knocking over dominoes. Every additional ally made me relatively weaker. One direct damage specialist was nice for knocking over the first cow, but past that, the game incentivized me to be alone with my exploding corpses.
There were definitely situations for which grouping was a better option, but it sapped my favorite activity in-game.