ramo is right
It looks like you'll be dead by T5 a lot. Your 2 and 3 mana removals (8) want double black, as do your 4 mana sweepers (5). If you stumble on that double color you're probably letting your opponent gold fish on you, which is doom vs any competent build. Suspect the three losses you mentioned are due to that. I'd look to replace some combination of Murders/Grasps with a playset of
Fatal Push, which would help you manage early threats while being easier on your manabase.
I don't understand what Siphoner is doing for you. I love the card in aggro or midrange, but in a control or ramp deck it doesn't make much sense to me, and your deck is trying to be both. Also you're not running any additional energy sources to help draw more cards.
Walking Ballista would make more sense IMO.
I think Rags // Riches is trash. You're super crowded in the 4CMC spot (13!) and should be looking to thin that out - I'd cut Rags first, then cut a few more. Maybe look for more things in the 2-3 CMC range for extra options to freecast with Expertise.