Every single level is doable on Easy (quite easily). I will post some tips below but first my times. Asterisk next to a level means that I completed the level on "Normal" mode (for whatever reason).
Cairo Station*: 10 minutes, 30 seconds
Outskirts*: 12 minutes, 22 seconds
Metropolis*: 11 minutes
The Arbiter: 9 minutes, 53 seconds
The Oracle*: 20 minutes, 33 seconds
Delta Halo*: 14 minutes, 09 seconds
Regret: 14 minutes, 38 seconds
Sacred Icon*: 13 minutes, 21 seconds
Quarantine Zone: 9 minutes, 23 seconds
Gravemind: 18 minutes, 19 seconds
Uprising: 4 minutes, 41 seconds
High Charity: 4 minutes, 54 seconds
The Great Journey: 11 minutes, 06 seconds
I got all of these times on my first attempt for each of them. This is excluding Regret, obviously, which is the speed-run I had the most trouble with out of any of the games. Some tips for completing the runs down below;
+ Dodge enemies - most enemy encounters are entirely optionable and you can generally just skip them. On Easy mode, they barely do any damage to your shields so just dodge them.
+ Grenades are your friends - these are really useful for clearing out clogged doorways. Spam a couple of grenades and watch the enemies move out of the way. Run through.
+ Don't stop moving - you'll find, on Easy, your shield will never deplete if you use tip one. Even if it does, you still have some 'health' to also chew through. My advice for most parts is to never stop moving. In a forward direction.
+ Know your levels - by this I mean know where enemies are and where you need to go. It is also VITAL to know if an area NEEDS to be cleared before you move on. There aren't many areas but there are still some. Know them and know how many enemies. I recommend doing a skull and terminal run first to get to know the layout.
+ Know any level glitches - it is not detrimental to know this but it definitely helps. Know where you can glitch out of the map and run around. This was useful in Gravemind (taking the route where the doll and skull spawn - up and around) and Outskirts (following the IWHBYD checkpoint route skips a whole lot of waiting around).
+ Use Vehicles at any given chance - this is pretty commonsense but in any area that is open and there is a vehicle, use it. It takes a second to get in and it shaves countless seconds which leads me to my final tip or piece of advice...
+ Every Second COUNTS! - Keep an eye on your timer (set it to "time" or whatever in options when loading up) because you're going to need to be fast in most levels. Do not waste time picking up weapons or trying to climb a piece of geometry that looks climbable (it's probably not).
It's an easy achievement to achieve - just keep at it! Regret is the only difficult level to speedrun because of all the ridiculous trams and such. However, if you glitch the phantom that drops hunters off at the beginning, you can save about a minute which is vital (which just put me under). To read about that strategy; go to the 'I Regret Nothing' achievement guide. Some nice person put a guide up on how to glitch it out of existence.
If you have any more questions, feel free to comment and I'll do my best to elaborate how I completed the area in which you are having trouble with!