Scent, Tremorsense, Blindsense, Blindsight, Detect Thoughts, Detect Hostil Intent, Detect Magic, etc....
Even without rolling an opposed check, there are many things that can get past Hide in Plane Sight.
Plus, if you really want Hide in Plane Sight, just wait one more level and you've got it on this build.
Cloistered Cleric 1 / Scout 3 / Ranger 16. At level 21 you'd have Hide in Plane Sight.