Indeed. Though I will say as far as bankai goes, his was probably the weakest for a captain. His dome would have probably have done more harm than good to him in most situations if he was fighting other captains in bankai. For example:
Vs Byakuya: All Byakuya has to do is surround himself slightly in a mini Gokei to defend himself and then just have his millions of blades fly around the dome until Tousen is eviscerated. Or he could just use those same blades to break the dome then eviscerate Tousen.
Vs Hitsugaya: He would really only need to do one Sennen Hyorou and those ice pillars would probably pierce through the dome allowing him to see again. Then he would just use one Hotten Hyakkaso and Tousen is finished.
Vs Kommamura: The size of his bankai alone would be enough to break out of the dome.
Vs Sui Feng: All she has to do his fire her missile any direction and he would die from the nuke explosion being trapped in the confined space. Sure Sui Feng would probably kill herself in the process since she would be trapped with her explosion as well but I digress she'd still win.
Vs Kensei: All he would really have to do is perform one of his wrist blade energy blasts that cause massive wind explosions, I think it's called Bakudantsuki. He just has to make the blast radius as large as when he was fighting Wonderwise. Sure the video cuts out before it shows the true size of the explosion but it was enough to eclipse the city for a brief moment and was more than enough to fill the dome. Hell...even Kensei just spamming a bunch of wind blades could do the job. If none of that worked, all Kensei would have to do is wait for Tousen to impale him like Kenpachi, grab hold of his sword with one hand, then punch him once with his bankai. The infinite explosions coursing through Tousen's body would finish him.
Vs Mayuri: Literally all he has to do is have his bankai fill the dome with poison. Tousen dies in minutes.
Vs Kenpachi: We've already seen this. I don't need to explain it. Kenpachi wins. (Obviously)
Vs Yamamoto: I don't even need to explain this. Tousen literally wouldn't even be able to touch him. I don't even know why I listed this. Yama could beat him in shikai.
I could go on but as we can see the vast majority of bankai that the captains posses could easily counter Tousen's bankai hence me considering his bankai and Tousen to be EASILY the weakest of the captains based solely off his shinigami powers. To me it makes complete and total sense he received a resurrecion and hollow mask from Aizen. In all honesty if he didn't receive such a power up, any fight he would have entered into with another captain would not have ended in his favor. Hell, more than half of the Espada could have probably kicked his ass. While his resurrecion is mediocre and ridiculous looking, it is really the only thing that made him a formidable captain class opponent by the Arrancar arc.