FormerlyHemlock
Hero
I agree with this for 4E. Almost every single fight, some PCs were bloodied and possibly unconscious and the foes were mostly ok. But with Healing Surges and healing spells, PCs became non-bloodied and attrition wins the day. Action Economy eventually shifts in favor of the PCs. It starts out against them because foes tend to use their encounter and daily powers immediately whereas PCs tend to start out with encounter powers (and only pull out Dailies if the encounter appears to warrant it).
In 5E, the typical story is different. In moderate fights, the PCs tend to have better AC, more spells/abilities, and similar hit points. So action economy shifts into their favor practically from the start of the fight. This is why healing is rarely used in combat except against tough or harder encounters. The fight is often over in 2 to 5 rounds (difficulty dependent) and PCs are not unconscious too often in hard or easier fights (although it can happen).
In order to get a near equal fight in 5E, the ACs have to be similar, the hit points have to be similar, the number of foes has to be similar, the damage has to be similar, and the to hit bonus has to be similar.
And the special abilities have to be similar or of similar value. If one side can teleport and fly and Web and Counterspell and the other can't, that's not going to be a 50/50 fight even if there's HP parity.
Count up the XP sometime for fighting your mirror image. The fight will be way beyond Deadly by DMG guidelines, because 5E tries really hard not to give you fights that have a 50% chance of total party annihilation, and by definition a mirror image fight is 50/50.