The tanking ability with the rescue ranger is pretty poor compared to the wrench. Definitely won't tank very much before the engineer is forced to pick it up, at which point you might as well switch to another class if they are pushing because you are useless as an engineer if you don't have your sentry up, especially if you don't have the shotgun. It does provide more options but it's not really that OP.
aci mean if ur teamates are calling their dmg why the fuck would u need ur med to call who s weak and who s not using the vow ? i m probably wrong but i think most medics would stick to the ubersaw anyways.
I would play with the solemn vow, simply because it's not actually possible a lot of the times to know if the enemy has built poorly. A lot of the times you are with the mindset that you have equal ubers, but you might actually have a big uber advantage, or maybe you have a disadvantage because they have been arrow building. You don't get ubersaws that often so it's not worth running it if the solemn vow is allowed.