how about light aura gives resistance

Instead of it giving 2 seconds of retal how about it gives 1 second of resistance, now the class that uses resistance the most that being the current meta SB actually has very limited ways that it can gain light aura so it balances out its potential for stacking more resistance making it still susceptible to necros boon strip on the flip side classes that currently have a very hard time dealing with scourges shades can apply light aura to them selfs with relative ease with the balancing part being time spent applying the aura to ones self and the skills wasted to do such a feat and in the case of radiance runes a whole rune slot taken.

the main concern is how well some classes could stack up the light aura, an engineer and my main for example using holosmith and runes of radience would have little to no trouble upkeeping perma light aura so some balance changes to how much light aura can be applied or how the resistance is applied would need to be looked at, perhaps changed to 2 seconds of aura on the leap and a 2 second cd on the resistance application and the duration to 1 second to force a certain skill rotation and maximization to require boon duration and to allow for strategic play for example my best source of light aura would be from using elixir guns super elixir and hard light arena to upkeep a long duration of light fields that i could use leap finishers in to apply light aura, i would need to use sword 3# followed by holo forge 3# repeatedly inside the light field aswell as taking spectrum shield for its toolbelt skill to maximize my upkeep on light aura now these light fields can have really long duration's in the grand scheme of things but also locks me out of other equally useful skills with the potential for countering being the necro just dosent sit in a position that allows me to utilize my light fields and other classes can put down alot of light auras(looking at you guardians) so this also complicates how appropriately balance for it can be achieved but also on that note opens up some notable team compositions and strategy's and a harder push on playing as a team, which could really pump out alotta salt in ranked atm haha but that aside.

on the flip side you could nerf spell breakers revenge counter and remove the resistance on that making them much more easier to take down in a 1v1 situation or if it dosent have the proper support from team mates but also allowing the warrior to maintain that resistance and potential more of it more appropriately from utilizing the many leap finishers at its disposal in light fields supplied by team mates with the balancing factor being forced to take specific weapon sets, and with more classes being able to run such a counter to scourges this would also force scourges to think more about how much personal defense they require overall lowering the total condition damage output they can take therefore creating a decent point of balance between the classes without having a direct nerf or buff to the class itself, i can run a glass cannon build on my engineer and can 1 combo necros but im a paper bag that can be easily taken down by thiefs warriors rangers and just about anything that dodges at the right time and that should be the case for anything that deals a shite ton of damage and in this case for necros if you wanna run a condi bomb expect to be a paper bag that gets taken down by any dps spec that can pump its self full of resistance which when people work together is engis/warriors/thiefs/rangers.

anyway i think its a good approach id say some people will disagree and some will agree but overall hopefully some of yas have a way of realistically decent balance

I think you are overthinking the problem. Only a few condi builds are causing problems so the most straightforward solution is to just tweak them the same way S/D condi Thief was. Introducing more powercreep isn't the best answer. Resistance is probably the second strongest boon next to stability, giving it to light auras would just turn Guardians into the new Spellbreakers.

How about not? Mesmer is already a very tough class to play against DH. Such a move would make a dh largely immune to my damage as well. No, it is not a good idea to make one class close to invincible against another.

Instead of just adding in more resistance, which is nothing short of powercreep, why not tone down the condi skills/traits that are overperforming instead?