Heath has his talkative moments, like that druing the Lunatic Fest interview whe he bubbled about Luna Sea members happily, much to the surprise of his bandmates, or during that comic con instance when he told the story of the band going to watch cows on a farm and getting lost in a forest
. I don't think he is that much of an introvert, he is a stage musician after all. He used to be a lead singer in his own band before X, he has solos, where he appears not-quite-so-shy in his music videos and his solo concerts are
wild as far as I can see from youtube instances.
He really doesn't seem reserved when he is doing stuff outside of X Japan. Maybe it is just his odd position in X that makes him feel uncomfortable. With all that shit he has gotten from Taiji admirers, I am not surprised he is trying to below key in X.
Social media is not for everyone, Pata has a facebook page but hardly any communication apart from some gig related photos and news posted by - no doubt - his management. Not everyone is as tech-savvy as Yoshiki and Sugizo and Toshi are. Sugizo also doesn't really communicate in English, most of his posts (lik,e 97%) are in Japanese, and Toshi is almost excusively posting in japanese only, using a few random English words here and there.... I don't see anyone but Yoshiki communicating wtih international fans.