Update...
Level 13
Heroes:
Hawkeye 19
Iron Fist 19
Wasp 18
Vision 16
Groot 14
Black Widow (new) 10
She-Hulk 10
Hank Pym 9
Drax (new) 7
Story Chapter 3
PVP Rank 15
Spec Ops 1 - Task 14
Some brief notes...
1. On your 7th Day, you get to choose a new character from Black Widow, Captain America, Hulk, Iron Man and Thor. Reading comments online, it looks like Iron Man is the best of the bunch. Especially for PVP. However, I went with Black Widow because I'm working on a Marvel Knights/Heroes for Hire type of team.
2. When doing Spec Ops Task 11 (Masochist), I found it beneficial to go through SO Mission 2, following the Hydra trail. Just be sure not to accidentally kill the Bruisers before they put up a Protect buff.
3. To conserve energy, when you finish Task 11, go ahead and ditch Mission 2 and go into Mission 3. Unless you have any heroes deployed.
4. Crossfire (the last Boss on Mission 3) is actually pretty easy, but the two goons right before him are tricky as they swap Protect back and forth. It's useful to have area attacks and/or a hero that can attack protected targets.
5. I've been pouring my Silver into ISO cannisters to level up my heroes since I'm focusing on Spec Ops and they don't get any XP from it.
Again here's the complete list of Spec Ops Tasks and requirements for each.
And here's a guide to the Daily Tasks.
Btw... I glanced at their Twitter feed and it looks like Valkyrie and Sif will be two of the next heroes added to the hero pool.