The Liches might actually work pretty well because you also have Mortarpod. In my list the only artifacts I have are Lashwrithes and Vault Skirges, so I decided not to find a place for them, because having one with a counter on the Vault Skirge is just too fragile and the lashwrithe is a 4 drop so it would mess the curve up. In your case though, you have mortarpod as a 2 drop so with the right hand it would work great. But even with that in mind, you don't need the liches to make lashwrithe good. It shouldn't be underestimated. It can take a mana flooded situation and make it into almost a good thing because they can get ridiculously huge. Also depending on your play group, you might want to consider Porcelain Legionnaire in the sideboard because I am also mono black and several people in my area run Mirran Crusaders and Swords of Feast and Famine and both of those can make the game pretty much over. Do you have any mana issues with the titans and only running 21 lands? I know there is a lot to read there. I hope some of it helps. haha
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Lashwrithes are great in mono black before they rotate anyway.
If you decide to go mono black it can add a lot of things. You will lose counters, but it can speed up your aggro a lot. Things like lashwrithe are great. It allows you to consistently cast Geralf's Messenger turn 3 which is something you really want. Also if you go that route you can still have a Diregraf Captain type effect from blood artist. The blood artist is better in the way it happens from all creatures and not just zombies, but you will lose out on the +1/+1. Blood Artist can also be better since it is only a two drop so you can get it out a turn sooner, which can mean more than you might expect. I have personally switched to mono black and love it. I hope some of this helps you in decided whether or not to go mono colored.
You might want to find a spot for a few Full Moon's Rise. Some Rootbond Crags would help your mana base as well. Other than that, it looks pretty good.