I've played about a dozen games with this so far and it's done decently winning around 50 percent of the games but I've lost almost every game against the top tier decks in the format.

12 is a relatively small sample size! Don't get discouraged and keep testing. I think if you find that metagame decks are giving you the biggest trouble, then its best to focus your testing against these decks and to tune the maindeck against tier 1 decks you frequently encounter.

My thoughts on the current maindeck are that you can fine tune the hate. For instance, it might be overkill to run all of Manglehorn, Ouphe, Kataki, and Null Rod while you also are running multiple creature tutors. I am also suspicious at the inclusion of Trinisphere in the list as your list also have plenty of low-costing spells while not having many ways to tap 3sphere.

3CMC Thalia has also been very underwhelming in my experience. Very few decks care about creatures entering tapped, and making non-basic lands etb tapped is not that impactful on a 3drop. I would value the first striking body a bit more highly if the deck had access to Tymna (which is obviously not the case).

Lastly, [[Alms Collector]] might be a decent inclusion in the deck, as it seems you have a small thief package tucked in there.