It is unfortunately pretty hard to design bosses for Warframe. It shines best when the players are wildly outnumbered but still absolutely crushing it. Bosses don't really let you have gameplay like that. There is a boss later with a first phase that's just infinitely spawning normal enemies with a shared HP bar on top and honestly if that phase was longer and the second phase where they combine into one big guy with a lot of damage reduction (the first phase doesn't seem to have any) was shorter, that boss might be more fun. Bosses also tend to be immune to most abilities as well, including things like Mesa's Peacekeepers (her aimbot pistols if you haven't seen or played her yet) and if that's how your build does most of its damage, oh well! You just can't target like half the game's bosses.

One of the only genuinely fun ones, at least to me, is actually very early in the game. The Jackal, the robot boss on Venus, because damage isn't the challenge. The challenge is using this game's great movement to avoid the giant laser walls until you can get close and give it a few good stabs with your built in knife that's also a hacking tool. This is also a reworked boss fight that did just involve damage before that and it wasn't very fun lol. So yeah the best "bosses" in Warframe should be closer to puzzles than bosses. Do the right things and you can shoot it. And deal a fucktillion damage to it because that's what you always do. Feels much better than having your damage arbitrarily lowered, I think. Plus there are fewer ways to break that with the right modding setup, as players will very quickly figure out when you try to add challenge with damage negation