'largely useful' is correct and usable in written English.
You can use it to describe something that is beneficial in a great many ways. For example, "The internet has proven to be largely useful for students, providing easy access to vast amounts of information."
These qualities may be largely useful and mechanical, or they may be largely athletic, or they may be largely grand and spiritual, or they may be largely emotional.
We believe that MDWiZ will be largely useful to the molecular dynamics community.
Although largely useful, physiology alone could not clearly and robustly identify the pathologic processes seen in COPD.
This indicates that this protocol may be largely useful for inducing sex in a wide range of related species including several of industrial importance, such as P. camemberti.
Whereas on one hand genomic instability is largely useful to transformed cells by providing a progressive growth advantage and development of drug resistance; on the other hand it may create exploitable vulnerabilities.
Fingerprints and structural keys are really useful for fast matching of similar structures and have been largely used for screening large molecular databases.
Spilman's prepared remarks consisted largely of useful, realistic advice about how to delay the cognitive decline most of us will experience at some point.
In large part, the schools are not providing the training that benefits law firms, so we begin with new graduates who largely lack useful skills.
TH-MYCN mice are excellent model for human neuroblastoma study, thus our results will largely be useful for facilitating the pace of neuroblastoma study, including in the study of the tumourigenic process, and in the development of therapies to treat patients suffering from neuroblastoma.
Visual comparison of the maps is obviously the most useful criterion, and that is indeed the criterion on which the authors have largely relied.
The balanced budget vote is a largely symbolicaction, potentially useful in re-election races for conservative Republicans but unlikely to get enough Democratic votes to pass.
