I am short on time so I will be brief.
Keeping yourself alive can be easy if you just use your head and maybe decent gear. Keeping yourself alive in the midst of your team causing a ruckus can be a bit irksome. However, have you ever tried to keep someone else alive who may lack either the experience or overall ability to stay alive themselves?
On occasion I have played the under-equipped miner in dangerous territory only to test the knowing knight's ability to protect someone else at their expense. Sometimes the execution is ugly even in light of successful results (in short, they may die at least once). But when trying to guide someone else who may not be prepared for the danger, my results are rarely satisfactory.
Truth be told, I have a habit of keeping less than sufficient gear for any run on hand as a part of the challenge. Some of that is due to preference. Some of that is related to what I can afford when compared against my in-game priorities. Either way, while I try to be the best possible example of what to do and what not to do (e.g. I mimic my party member's gear in-utility to give a better idea of how to fight with it), and in knowing that some of the responsibility of their survival depends upon them, I am almost considering giving into the use of more favorable weapons among knights merely for the greater damage output; that seems to equate to faster results.
So I will close with this. Keeping myself alive is never difficult if I keep my attention to what dangers approach me. Keeping alive among other capable fighters who may or may not know how to play well together is enjoyable in its own right. Yet, when providing guidance, tanking shots destined for the unknowing, displacing, and even slaying enemies, how else should I keep someone alive in dangerous situations that is not prepared for it without any sort of revival or death occurring?
This is a great topic for a thread. Defending weaker players is a fun game in itself.
Shield-bump the monsters away from your weak teammate. Shield your weak teammate while he shoots at the monsters from within your shield. Also shield-bash monsters away from him.
Bomb non-disruptively around your weak teammate, to interrupt all nearby monsters. Dark Briar Barrage is good for this, unless it causes your teammate lag. Nitronome is good, if your teammate doesn't mind the total chaos.
Out-DPS your weak teammate, to draw the monsters toward you. Ash of Agni is good for this. Then he follows along taking pot-shots at them from behind.
Damage a trojan until it is near death. Then draw its attention while your weak teammate gets a chance to kill it safely from behind.