Design for Bosses' Survivability (In an Engaging Way)

[CriticalFumble]

I feel like there's three somewhat abstract generations of bosses in Warframe. 

There's the 1.0 bosses which are just elite fodder units, exceptional stats, same weak points, and possibly a few unique powers.  This is the most concrete generation and are almost extinct - to the point where Phorid and the Sergeant stand out badly.  

Then there's 2.0 bosses who have unique models and fight patterens.  For instance, Vor, Krill, and the Hyena Pack.  They also have health gates at least, if not invulnerability phases to extend the fight and make it at least appear more intense and challenging.  In the case of the Hyenas, there being more than one target functions as something of a health gate.  

Finally, 3.0 bosses have everything the 2.0 generation has, a distinct and unique arena tile (rather than specific or just unique) often with its own hazards, and a grab bag of other factors like odd ways to make the fight get back going (Kela) secondary forms (Lephantis) and non-linear ways the fight must be finished (Raptor, Ambulas).  This is all somewhat nessisary to keep Assassination missions from being done at the speed we do Capture.  What with the arsenal many of us use that would make the Death Star feel inadiquite. 

What seems to be the final answer to directly countering the DPS monsters we've become is things like the Hemocyte.  Noticable armor that can't easily be exploited (like the Eidolons), health gates (the heads), invulnerabilty phases, and a damage limiter to cap it all off.  This would be all well and good, but its just not fun to play.  You either just go and slog through it, or you optimise for the fight and end up feeling less like you're figting the giant monster than the game systems around it.  

My suggestion would be to make it have the boss react to player attacks rather than just making a system to negate them.  For instance with the Hemocyte's DR ability, instead of simply capping damage recieved, let those kinds of hit have some secondary effect, like a flinch that extends the damageable window; or have damage beyond a certain level cause it to either go invulnerable for some time or trigger the damage cap effect for some time.  

Elsewhere, modifying the idea behind the Sentient immunity health gates could produce some interesting situations.  Build a way for the AI to determine how it is recieving damage and give it a counter to it.  For instance if it was hit with a sniper round, it gains the ability to defelect a certain number of projectiles in a window of time.  Getting pummeled with lots of weaker bullets makes it deploy a shield, or getting hit with melee weapons encourages it to jump over spin attacks, kick face huggers, and such.  Maybe even dynamically alter the arena based on what's happened.  

Summary point:  Making boss fights significant is good, and difficult given the power level players have in Warframe, but hobbling select player tools, especially without warning or explanation, is bad.