Takenaka Hanbei is probably the tank you're looking for, at least among SSR generals. Naoe Kagetsuna is pretty good, too, and has a very nice team buff in addition to her tanking abilities. Hohjo Ujiyasu, Honganji Kennyo, and Toyotomi Hideyoshi are also serviceable tanks. All of those have high leadership ratings and a self-healing skill.
Really, though, tanking becomes less important for PVE as you get stronger. You don't really want to draw out a battle across 5 rounds of combat and eventually win. You want to kill opponents before they even get to attack, and tanks don't help with that unless they're carrying a good team-wide buff. Faster battles means that you can do a lot more of them in a day.