...Is there a question besides the one about Therapist, or are you just venting?
Wild animals, especially predators, especially
large predators, can be fairly dangerous. You pretty much need armor on every body part, including hands, feet, and head. Full copper armor should be enough to survive. Also, shields are the most important piece of defensive equipment; a shield will block between 1/4 and 1/2 of all attacks on a skilled shield user, so they're better than armor. Finally, hammers and blunt weapons are meant for armored targets. Blunt attacks are comparatively ineffective compared to edged attacks, mostly bruising or at worst breaking bones, but when armor comes into play edged attacks can be treated as blunt attacks and due to their physics edged weapons don't make good blunt weapons.
Depending on how large the squad was and how many of them attacked the crocodile at once, they shouldn't have had too much trouble if their skills were decent. Have your soldiers actually been on a training schedule, and have they actually had a barracks set up to train in? Those are important. Also, the fastest way to train if your military is entirely unskilled is in 2-3 dwarf squads, as the low numbers encourage sparring.
I don't think you can assign dwarves to the military with Dwarf Therapist directly. However, there is a workaround. Give dwarves that you want to be soldiers in a particular squad a custom profession name, something like "Warrior 1," and then go into the military screen and put all dwarves whose profession is Warrior 1 in one squad, all "Warrior 2"s in a second squad, and so on. This will let you fill squads relatively easily, as you can quickly identify who is supposed to be in what squad and you won't accidentally try to assign someone to 2 squads.