IME, unlocking soulbound weapons can be tedious, but it is hardly something I don't have enough enemies left to do.
Some quests could be left behind to speed up the process, if that's an issue. For example, in my last play through I left Raederic's Hold behind and went back to it when I wanted to unlock Steadfast and The Unlabored Blade. For St Ydwen's Redeemer, there are plenty of Vessels in the Endless Paths of Od Nua, as well as Heritage Hill and the Sanitarium.