Hello Mc.V,
So one quick bit of housekeeping: what you are calling combo's are referred to as stacks locks in the commander community. When you say combo in commander it usually means a set of cards that wins you the game immediately. As opposed to stacks locks which stops your opponents from playing the game. Stacks games can go on for hours if they managed to stop your win con before you locked them. If you ever intend to play this deck with other people, please be up front with them on what the deck does. Stacks games are not fun for people that aren't prepared to deal with them.
With that out of the way here's a few card swaps I would do:
1)
Silence --->
Render Silent2)
Steel of the Godhead --->
Unquestioned Authority3) Hanna, Ships Navigator --->
Mistveil Plains or
Hall of Heliod's GenerosityYour list has a few awkward cards, that you can definitely play but may nonbo from time to time.
1)
Monastery Siege and
Spirit of the Labyrinth. On their own their fine, but with both you draw and discard as opposed to draw 2 discard 1. Given you have multiple locks that stop your opponents from playing, I'd suggest cutting Spirit.
2)
Island Sanctuary does work in stopping ground attacks, but if an opponent slams a hasty Drakuseth, Maw of the Flames your in trouble. If you want another Zur target I'd look at
Propaganda.
3) Lightning Grieves is a bit awkward because you are trying to get 2 to 3 aura's on Zur. This card is fantastic if your not on a Zur damage win con. You may want to look into
Mask of Avacyn instead.
4)
Desolation,
Mana breach, and
Overburden are all very dangerous cards to have out if Zur dies and you cant re cast him. Look instead at
Back to Basics and
Mana Maze for mana based disruption. If your play group isn't very removal inclined, you can keep these in.
One last general note: This deck should have about 2 more rocks and 8-10 more pieces of card draw, because if someone powers out a turn 2
Nevermore or
Phyrexian Revoker naming Zur your deck needs to function without him. Right now your card "draw" is Zur fetches and tutors, meaning you gain very little card advantage off of
Monastery Siege and
Brainstorm.