"been seen to be" is an idiomatic phrase that is correct and acceptable to use in written English.
For example, "The evidence has been seen to be overwhelming."
It would have been seen to be less serious.
'We have been seen to be a leader.
For alginate chitosan complexes, the binding enthalpy has been seen to be −3.49 kJ/mol.
In earlier studies, thermal responses have been seen to be sluggish.
Since his appointment in March, Pope Francis has been seen to be advocating humility.
The powerful had been seen to be no better than the rest of us.
If only he had been seen to be doing more to tackle those underlying grievances.
But anyone who simply proposed that would have been seen to be blowing smoke.
Given the opportunity to make his case, Stanley may have been seen to be deserving of custody of his offspring.
Results of the ESs have also been seen to be comparable with the experimental results reported in the available literature.
The learning environment for doctoral studies has been seen to be an important factor affecting the quality of doctoral education.
