Dry ice requires better handling practices, and costs more, but not as much as a lost customer or ruined product that you have to replace.
Last I knew, there are two companies working the Canadian mysis harvest, PE being the one that has invested the most in post harvest handling. He ships direct to LRS, so if you get from LRS, you can feel confident in proper handling. LRS sells Hikari and PE.
Mysis are like the canary in the mine.... if your mysis are in pieces, they got too warm, plain and simple. They were harvested whole.
When buying cubes, look at them if you can. They should be flat, no ramped up one side of the cube
Capelin roe is awesome. I'm sure Tim's is just fine. You can buy local at Ranch 99, etc.
When RN was developing ROE, capelin was one we looked at. Sourcing was an issue though.