I've been sitting her 6 hours and caught over red caps on high road but not seen a single sea fairy . . . epic or not, it should not take this long
When I do the Avalon fishing quest I always go to High Road for the William Walleye (only found on High Road) but I start with a reveal fish school to check if the Sea Fairy happens to be there (only life fish there). If no life fish show up I winnow rank 2 and catch a balance fish - the only rank 2 balance fish is William Walleye.
Then I move to Dun Dara and do a winnow death, then use a rank 3 death lure - that fishy is either Hamlet (that we need) or a Black Knight Bass (rank 3 epic fish). Outwith the fishing quest I'd cast winnow rank 3 and see if the fish left were ice, death or storm as all of them are cool fishes (but only the King Mackerel is needed for the quest and can be more easily found in the Wyrd).
Then I go to the Wyrd. There are 2 spots for fishes. I almost certainly need 3 fish here - the sea fairy (rank 3 life), king mackerel (rank 3 ice) and the hag fish (she's a rank 2 death sentinel).
I do a reveal fish school at spot 1 and look for life or ice, if there is no joy I run to spot 2 and do the same...repeat until we find one (or both). When I find an ice or life fish I can winnow the rest and catch it. I might need to catch a sentinel to get it out of the way (woohoo hag fish ticked off). I just repeat the process of reveal at each spot then run to next and hit reveal, then reset and reveal, run back to the other spot and reveal...it's long but on zero energy fishing we don't hit the energy limit at least...I've done this without zero energy fishing too and still think it is the easiest way for the quest.
As for the swordtail, I usually grab him down in Caliburn since it at least has cool items in the chest if it takes a while to find him lol. I might see if he is in Caer Lyon too but I tend to get fish and chips...and no luck on chests.