I think it's more versatile, compared to unsummon it's bounce any nonland perm instead of just creature, which I'm sure excluding plainswlkers and detention sphere it won't make a huge difference, but there is one still, and also it has the overload potential. Also you are already playing pillar and slip for 1 drop disruption slots. So you aren't slowing down really by adding a few 2 drops. I mean unless you lose by turn 4 a lot in your meta, rift is the way to go. Also I would consider switching the rift for the slips. Slip is good but dependent to be great. It non combos with pillar since the exile effect doesn't trigger morbid.

ALSO after reading your other comments, I just want to put it out there that I am a bug/rock player myself. (except in edh where I am red for the most part)

I can see your point with the synergy between the early drops. I'm definitely considering dropping tragic slip now for cyclonic rift, but I'm not sure whether or not a two of would be too much or not.

I run 2 Unsummon and 2 Cyclonic Rift I have found that stalling the game out is a lot of fun and seeing the annoyance on my opponents face when they've cast the same card a few times just to eventualy have it countered is very satisfying. I would try to fit Far / Away in the deck. worst case a 2 mana unsummon. best case a 2 for 1.Also Chandra, the Firebrand would be cool as an extra way to get the 1 dmg in after master of cruelties does his job. Plus Im prety sure that split cards are 1 spell so if you use her -2 and fuze Far / Away you got both halves twice. not much other use out of her that i can see with your build though. your instants would probably be better served at instant speed and not on 1 of your main phases. +1 LOVE grixis.