O.k, imma give a rundown of all Squad Members for ME2, since I don't have ME1.
Jacob Taylor-Absolute joke. I like his personality a bit and find his romance to be hilarious, but I can't count a single time where he's been particularly useful. His weapon selection is crap, he doesn't have a single direct damage ability and his loyalty power is a more useless Fortification or Geth Shield Boost. 0/10
Miranda Lawson-In contrast to her colleague Jacob, Miranda is a squad member who fits in almost every situation. Warp and Overload are good against almost any type of enemy, although I don't really see the point of Slam. Her Passive ability is nice too, giving your entire squad increased weapon damage or health. I tried not to use her too much, as I needed to give my other squad members some time too. 10/10
Mordin Solus-He's very good at what he does, which is anti-armor and crowd control (somewhat). He's pretty squishy and tends to die a lot if not babysat, but Heavy Incinerate really does a number on those Scions and organic enemies in general. 5/10
Garrus Vakarian-An all around great squad member. Overload and Armor-Piercing Ammo are useful against shields and armored enemies, respectively. Concussive Shot is another great ability that can disable an enemy for a short amount of time, but also has the upside of making Pull a much better ability to use. Weapon selection is great, too. Sniper Rifles are always the best choice for squad members. His only real problem is that Armor-Piercing Ammo isn't at good as an ability such as Incinerate, or even Incendiary Ammo. 8/10
Grunt-Another great squad member. His Incendiary Ammo is great for tearing up enemies (especially Blood Pack and Collectors), Fortification makes him extremely hard to kill and Concussive Shot is a pretty decent ability. Weapon selection isn't too bad as well. He suffers from no anti-shield ability and only one offensive ability that is useless against protected enemies. 8/10
Jack-Like Jacob, she's a next to useless Biotic. Shockwave is situational, even on lower difficulties where many enemies aren't protected. Pull is generally a poor ability with minimal use. Warp Ammo is the only decent ability, but it isn't even enough to save her from never being used. She also has the same crap weapon selection as Jacob. 1/10
Kasumi Goto-SMG's are good, Overload is great, Shadow Strike is amazing, Flashbang is good. Also, her voice and personality is fantastic. Most commonly used on "merc" missions where I would be facing a hodgepodge of enemies who have backs ready to be Shadow Struck. Only downside is she's squishy. 9/10
Zaeed Massani-Disruptor Ammo isn't the best, but it really shines on Overlord and other Geth missions. There aren't too many of them, but when it can be used, it really is a fantastic ability. Inferno Grenade and Concussive shot are good abilities in general, but nothing to fawn over. 7.5/10
Tali'Zorah vas Normandy-Combat Drone has saved me numerous times and is good enough to make up for her other 2 junk abilities, besides maybe Energy Drain. She has crappy weapons though. Give her the Geth Plasma shotgun as soon as you can. An all around average squad member. 6.5/10
Samara-Reave is the best Biotic ability in the game. Absolutely amazing against Barriers, Armor and unprotected (teehee) enemies alike. Pull is bleh, Throw is meh. She has a nice weapon selection that's a tad redundant, but still better than a lot of other squad members. 7.5/10
Thane Krios-I was surprised to find out he was a Biotic. A Biotic hitman is one of the most badass things I've ever heard of. Warp is always a useful ability, Throw has some use and Shredder Ammo isn't particularly stand-outish. Snipers and SMG's are a definite plus, pushing him a notch above others. 8/10
Legion-Are you kidding me? The first robot squad member, and he sucks robot nutz? A.I hacking is useless in almost any scenario and should never be invested in, ever. Geth Shield Boost is crap, way worse than Tali's loyalty ability. Combat Drone is the same as Tali's, a great distraction that can save you and make a big difference in an intense firefight. But it still isn't enough to make him a worse version of Tali. Not even his weapon selection will make up for the extreme disappointment. 4/10