It would depend on when they joined, but yes, some will know him personally. I'll also be mentioning this later on, but as well as being a peacekeeping force, the Dragonier also raise their own dragons and with wild dragons being exceedingly rare, its generally considered to be the [i]only[/i] place on Tirn where you can get a dragon and learn how to ride one.

Sifa left the Dragonier to become high queen of Avalan 200 yrs ago, shortly after the death of the last Elder Dragon, so I doubt your character would have known her from back then. It depends on how old you want him to be though, so I guess the answer is maybe. The numbers of the Dragonier have indeed dwindled over the years, but there are probably more former members than those actively serving atm, given the longevity of mages and certain races.

I can imagine some elves holding resentment against your character, particularly those who survived the battle. Still, others will understand that it probably wouldn't have made much of a difference. They were going up against a Paragon after all.