The phrase "as largely irrelevant" is correct and usable in written English.
It can be used to describe something that is mostly unimportant or not significant in a given context.
Example: "In the grand scheme of things, the details of the report are as largely irrelevant to our main objectives."
Alternatives: "mostly insignificant" or "primarily unimportant".
With its decline, many analysts have written Mr. Case off as largely irrelevant, lacking strong support on the board or among its executives.
The CSR road is regarded as largely irrelevant: they don't see the need to tick CSR boxes or proclaim their sustainability virtues.
If scarcely anyone is taking any interest in the general election it's not just because the result is seen as largely irrelevant: it's the markets that rule.
WASHINGTON — Just weeks ago, economists and financial analysts were dismissing Washington as largely irrelevant to the economy's course in coming months, if only because it chose to be.
Other Asian "tigers"—Singapore, Taiwan, Hong Kong, Malaysia, even South Korea and Thailand are relatively small places, whose experience it was possible to dismiss as largely irrelevant.
Father Brankin describes members of the liberal Catholic movement as lost souls, disenfranchised by both their own church and a larger society that views Catholicism as largely irrelevant.
Last time I looked, people were not lining up around the block to join me on the couch, where I'm perched as a largely irrelevant figure in America's mainstream discourse.
West Virginia, I'm sorry, is going to show itself as a largely irrelevant anomaly when the rest of the country expresses its wish for a new broom that will sweep clean.
The "digital exhaust" from internet use might be just as embarrassing and largely irrelevant to society as the refuse in our waste baskets.
Nigel Farage had been expected to grab between 75 and 100 extra councillors at best, but added nearly 130. Labour MPs and activists, who had tried largely to ignore Ukip's impending arrival as the fourth party in British politics, veered between admitting that it had been hit and that Ed Miliband had to do better, and trying to dismiss Ukip as still so small as to be largely irrelevant.
However, I have always tried to overlook those Right-Left distinctions as arbitrary and largely irrelevant -- one person's politics should not be so simplistic as to fit so neatly into such categories.
