I didn't know about that spell to look for the faq, that should solve the problem for this camp (a toggle for this would be nice, but I know your answer to that). Still if your group didn't have a shaman it would be nice if your character could tell when not to kill itself on a DS like a real player would, again wishful thinking. Thanks for the pointer to thorn wilting.
it can't tell. it doesn't know someone isn't going to dispel it or give them something that isn't going to ignore the damage shield damage.
you, the driver is responsible for that.
mq2rogue doesn't know if someone has a skull of null or another dispell clicky that they're going to use on the mob, they don't know if one of your casters is going to use eradicate magic on it to remove a beneficial buff
you *are* asking it to fight a mob you're asking it to fight, and it is doing what it is told
Q. Mob has a damage shield / I want to use Thorn Wilting?
^ that is a 2-parter; it says "what do i do if the mob has a damage shield" and "how do i use thorn wilting to combat against mobs with damage shields since i don't have other options" and the answer is "you can byos/byos-custom thorn wilting. it doesn't say "Only look here if you know what thorn wilting is called".
the way you're expressing yourself about this situation seems a bit misplaced.
if you're fighting mobs with damage shields and you're using characters that a: melee and b: use fast weapons max'd hasted and stabbing infinity times a second - you need to approach that situation with that knowledge that even fast heals aren't going to help you. that you need some way to negate/ignore/skip the damage shield. There are a lot of options for that
if it is a mob beneficial - you can use eradicate magic on a pure caster
if it is a mob beneficial - you can use a dispel clicky like "Skull of Null"
you can use debuffs on the mob like cleric Retort line
you can not have your melee character attack this particular mob
Terror's Juju is another good anti-DS item you might consider getting
your rogue is going to worry about rogue things - its job is to fight the mob it is being told to fight. it has faith that you, the driver, are setting it up for success.
for example - if you send the rogue to fight a mob that is most likely going to kill it - it isn't going to say "nah im not going to fight that" and just stand there. that wouldn't make sense
if you want your rogue to pause, or go in manual mode and turn off attack and clear target when the mob it is fighting has certain debuffs - you could utilize LEM (or mq2react - but i'd suggest LEM) to do something like that.