Dreadlords can speak truthfully - but generally only when no one else is around to hear it, and when the person they're speaking it to won't be in any shape to speak of it afterward (kind of like Saidan Dathrohan and his first meeting with Balnazzar). As for Varimathras it's always wise to treat any Dreadlord's pronouncements with suitable doubt - but as demonstrated here, even *that* has a tendency to sow dissension and discord.