Well, to be fair, in the fight with Tartarus, Johnson will outright tell you how to beat him. "His shield is down--let him have it!" And Tartarus does provide you with an audio cue to confirm that shooting him after Johnson downs his shield is the way to beat him. He says "A lucky hit. You'll not land another!" That makes the Tartarus battle fairly straightforward, and quite easily survivable on your first try if you play it right. In fact, I did survive it on my first try.
A bad boss fight by your definition would probably be the fight with the Heretic Leader. Against Tartarus you received the aforementioned tips. Against Regret, Cortana tells you to get in close and see what you can do, and if you follow this, the game will outright tell you: press X to board, press B to melee. His screams confirm that it's working. But against the Heretic Leader, you are by no means informed that his holo-drones are infinite, or of the method to keep track of the real one. You aren't even informed that you need a sword, camo, and the method to keep track of the real one in order to beat the boss without dying. Now, I have on multiple occasions beaten this boss without dying but the fact remains that on my first try, such a feat was outright impossible. That boss fight was a horrible experience the first time around.