The lack of invulnerability warframe

[Vortigaunt256]

When an operator exits a warframe, the warframe remains vulnerable.
When a warframe dies, the operator also dies.
However, if you also sit inside the necromech, then we lose the warframe. 
And if the operator dies, then he has a timer during which the allies can revive him.

The screenshots show that the warframe is vulnerable and takes damage.
And on the last one, you can see that I am reviving by an ally while I am falled in operator.

 

[Kherae]

lack of invuln is typically from having an ability active, instead the frame has a 90% damage reduction. however, that might explain why people are losing their warframe in open world missions; the warframe can die in that state.