Somebody calling the enemy weaker than us and a chance to make a post about numbers and mechanics? Let's do this.
On the higher difficulties of Mass Effect 3, the enemy is statistically significantly stronger than Shep is. On insanity a basic Cerberus Trooper has 1687.5 while Shep isn't really getting much higher than ~850 health/shields. Even Cerberus' weakest unit can match us for total hit points and the only enemy with less is the Husk at 928. I guess Swarmers have like 5 HP if you want to count that.
So surely the player can put out more damage then? Not exactly. The infamous Marauder can do 93.8 damage per hit on insanity, which is about 2.5x as strong as a Phaeston X that the player wields coming in at 37.2 damage. Even the Mattock X, one of our strongest non DLC Assault Rifles comes in at 95.2 damage per hit and fires slower than the Phaeston does. The Centurion that wields the Mattock? 245 per hit.
Most enemies in the game get to enjoy that damage disparity, except for the Geth Hunter. The Geth Plasma Shotgun does slightly less damage on insanity than our rank 1 version. Keep in mind the stats I'm giving for the PC are max level stuff, which requires NG+ to even get in the case of guns. At the start of a game, Shep is much weaker than this.
So what does this mean for how tough enemies are? Not much honestly. Give me Shep with a Mattock and I can take out a squad of 8 Centurions with ease, even completely ignoring powers and having no passives. This happens because I'm a vastly superior marksman to the AI and because I know how to exploit things like right hand advantage so I can shoot them while they can't hit me.
but Mass Effect is a game with powers, so what if we gave enemies powers? Okay, I actually like that idea but it's not going to solve the problem. In the Citadel DLC they gave us the option to play Mirror Match in the arena. For those who haven't played it it consists of three waves: Wave 1 is a Soldier, Engineer, and Adept. Wave 2 is a Vanguard, Infiltrator, and Sentinel. Wave 3 is all 6 at once. You can also turn on penalties for the player which include: Player shields are destroyed in 1 hit, no medi-gel, no ammo pick-ups, stronger enemy shields, and higher enemy damage.
Yeah... I managed to best that on insanity with no teammates and every debuff turned on.
I've also tried in MP giving the enemy aimbot levels of accuracy and it pretty much just turned the game into something that ultimately feels like the enemy is just cheating and the average player isn't going to enjoy playing. I don't see that as good game design, as most of us will just turn to cheese strategies like Nova + Biotic Charge spam for infinite damage immunity.
Mass Effect when played in real time is a skill based game, which means that the best way to provide a challenging yet enjoyable gameplay experience typically doesn't involve making the enemy statistically match us in every way.