If You Had To Cut 3 Squadmates from ME2...

She can indeed do the ventilation shaft during the Suicide Mission.

I still think Zaeed would have been 100 times more compelling if he was a Batarian. 

Having another human, who was the best in his particular field out of the entire galaxy, was eye rolling for me honestly.

Interesting perspective. Cutting out old friends to help Shepard keep a clear head is a sound strategy. It all goes out the window if he/she romances any of the new crew though. Because any worry he might lose to protect his friends will be present to protect his romance.

As for Thane, yeah he's a loner more than a team player. But since the suicide mission basically entails something we do not know, someone that can handle themselves against multiple enemies is not a liability. If we're talking functionality, Jack would actually be an easy one to cut out, considering she's unstable and all that. 

If we talk strictly function, the squad mates that are REALLY necessary for either the suicide mission or the plot progression in general are quite clear, and well, I think you picked two of them that are actually more important than you think.

Mordin is extremely valuable, obviously. No explanation required.
Garrus is too, I mean, how could we survive without his calibrations? Jokes aside, remember that you can't upgrade the Normandy's cannons if it weren't for Garrus.
Tali is what gives the Normandy the upgraded shields.
Samara offers more fuel for the Normandy in the mini-game, and even though this is a nice to have, she is required for the biotic part of the suicide mission. As for Jack, see the final list below.

Those above are the essential crew members.

A few crew members only offer 'minor' contributions that would fall in the nice to have category;
Thane offers more carrying capacity for probes.
Miranda offers faster scanning. And although she is the one that brought you back, she doesn't need to be a squad mate afterwards, since her main contribution is already done. 
Jacob, even though he allows the Normandy to have upgraded armor, which would fall in the above category of being extremely valuable, all that it ultimately offers is saving Jack's life, the most unstable character in the whole team.

And then there are those that offer nothing, or offer something that another character above already offers.
Kasumi
Grunt
Jack
Legion
Zaeed

Jacob and Thane are easy picks, and as much as I hate to say it, Kasumi would probably go as well. She's my favorite character in the series, but it's hard to justify a third human female who has no real reason for being in the squad and little significance to the story.

Point is valid but I suspect TIM thought it would be a true suicide mission and that none of them would return from the Omega-4 relay.

Story-wise,

Zaeed - Ex Dee

Jacob - Stale, and didn't add meaningful context to the universe

Grunt/Thane - I don't care for Grunt and Thane's quests that much. To their credit, as characters they did add new lore to the universe. Garrus' plotline was just a milquetoast revenge story, technically worse than theirs, but I'd prefer he be in the game over them.

Gameplay-wise,



Jack - a worse version of Samara

Garrus, Zaeed and Legion

Jack, Thane(doesn't even a role in the SM) and Jacob(although he's unintentionally funny).