Lesse, so your options were to do what you did, return and land above MLW or ignore severe engine vibrations and continue the flight?
Landing above MLW would have required quite a bit of inspection, with associated costs. Can’t say what it would cost, but probably more than what it did cost the way you did it.
To go on with the engine vibrations you had, well... if they were within limitations, it could be an option I guess. But if the “consider shutdown” was quoted from the instructions, that was not the case.
If it was known or not does not matter if noone told you about it. I’d be interested in hearing what they thought you should have done.
Cheers,
Fred