You need blink to complete the game at all in levels 6 and 7. To climb up the tunnels above the water lock, and to climb out of the cell/pit in the flooded district.
So you need to blink in those 2 areas to complete the game. 3 blinks in total I think.
Now if you were also playing for a ghost run, I don't think this changes. By ghost I mean no guards, guard dogs, weepers etc ever see you, even for 1 electricity bolt. River Krusts and rats don't count.
I'm playing through this exact way and currently on level 9. Successful so far. I haven't always gotten ghost because I like to rescue the innocent people from guards and so forth. So sometimes I knock out guards. But if you want to completely ghost you can always be a douche and ignore those encounters.
I suppose it would be pretty funny to have Sam go at the last mission "yeah mister Corvo, you're sharp because you managed to keep sight of what's good in all this mess" when you stood by and did nothing in mission 3 as an innocent woman was beaten to death by thugs, despite yourself being one of the deadliest assassins around.
Anywho, yeah you can ghost the entire game, get most of the loot (theres loads you can't obviously), runes and bone charms, and all but one Sokolov painting (nothing to do with ghost, you just need blink to get the thing).