Avi K, R Shalom Arush just put out a paper warning that it is assur to daven to a tzaddik. The “Tziyon Hakadosh”, a Breslov guide to the Tziyon, writes explicitly one may not daven to a tzaddik. I have gone to Uman many years, and I have never seen someon davening to a tzadik (asking him to talk to Hashem,, yes, which is muttar) but davening to him, never.
Its typical litvish am haratzus to think any sort of avoda zara is going on.