Sorry, but this is how Guildwork works and 1000s of people use it and 100s have paid to use the Premium version of it. Your virus scanner is firing because it tries to access the internet which is obviously needed to send your character data. FFXIAH also expects the Synergy to come from the plugin. There will not be any other way.

I can p. much vouch that any files coming to/from this are clean. This is a big scene, no one is out to hack anyone and most people have been using the new plugin since it came out without any issues.

That said, if you aren't protecting yourself properly, even visiting an ffxi related site can cost you your toon.