I should note that there were several NPCs asking to examine her new weapon while getting through Dalaran AND out in the wilds of Broken Isles. There was one northeast of the Illidari Stand flypoint in Azsuna which was marked by a star on the minimap BUT he turned out to be a friendly NPC who only wanted to examine the blade AND who gave me an artifact which boosted its score by 100 points. Probably after that completion I won't get any more requests.
After that getting that request in Azsuna, I had my mage return back to Dalaran and she did get another request from an NPC there to let him see the blade and got rewarded with a 50-point bonus (hmm...I don't recall this happening when she got the 2-handed frost legendary in the first place, nor did this happen when my hunter picked up BOTH legendaries for beastmastery and survival but then I had put both of those away in his bank very quickly and was still using his legendary marksman bow all during those quest chains). Perhaps this is a feature to partially help along any toon that does switch legendaries and maybe there will be other NPCs in other areas of Broken Isles who will make similar requests (at least until my mage's fire weapons "catch up" to some degree with the bonuses that her frost staff had).
I should note that unlike that first bonus from the NPC in Azsuna which was an item that my mage had to click on to add its bonus to her legendary fire weapons, there was no item from that NPC in Dalaran but the bonus was directly added to THAT legendary. My guess is that SOME people had figured out this bonus item system early on and done the lending of a "new" legendary weapon to those NPCs but then switched back to their usual legendary weapon before applying that bonus item (which, of course, is prevented by the automatic application of the bonus directly upon the held legendary weapon).
Hmm. My mage is my secondary "main" and I've always run her in and got her equipped to at least LFG raid level if not actual raid level gear (much less so my other toons who I view as support staff to supply items from those professions that neither my hunter [skinner/LWer] or mage [tailor/enchanter] have). Kirk, I suspect that you will find your frost mage to be more similar to mine if and when he gets to higher levels, probably starting with Lich King/in Northrend so around level 68 and beyond.
On the other hand: considering the slow progress that my HUNTER has had just trying to complete faction reputation and even basic quests around Broken Isles, it is going to be quite a while--MANY months into 2017?--before I start leveling up my warlock [herbalist/alchemist] who will be next (or maybe not if my guild starts regular raiding and fellow guildies begin to offer items like flasks and gems and such).
Oh, while my mage is running around in the mage guild zone, I almost never see any toons accompanied by water elementals (and thus frost) and only see other toons with fireballs floating around them (consequence of one of the passive fire spells). MAYBE there are some arcane mages but they are less obvious.