IMHO a lot of people dislike the name simply because it lacks "legacy". I'm pretty sure they'll try to create lore and personality for it, but for right now my reaction was 'meh'.

The "piratey" looking armour and beach/island/treasure setting is why a lot of people went with Corsair (plus Merylwb has animation sets for pistols, I honestly thought they were going to reuse them), it was the logical choice. But they decided not to have a gun/blunderbuss so that option went out the window. Would people have reacted negatively to a Corsair without guns? We can only speculate now.

Viper wouldn't have been my first choice. As some people on other threads have pointed out names like Thief or Pirate have "negative connotations" (fun fact: I worked on a game about pirates once and some countries really hate to use the term on titles, so it had to be changed to sailors or something).

I would have gone with "Treasure Hunter" as a wink to FF6's Locke. Too long or confusing? something like 'Raider' then. (As in Raiders of the Lost Ark, or Tomb Raider. Fits the setting).