@CmrToodles,
He's not really intended to be a sniper, the slower projectile speed almost rules that role out entirely. He's best played as Indirect Fire Support in the objective based game modes such as Turf Takeover and Suburbination, maybe even Gnome Bomb
With decent range, splash damage and good damage on a direct hit his role is best suited for standing off at mid-to-long range to bombard a target. He's definitely handy to soften up the defenses around a Garden or to help knock down a Plant trying to defuse a Gnome Bomb.
I don't think that there is a "worst character". What I know is that there are characters who I have not yet figured out how to play yet because they are best used in certain play modes, with certain play styles with certain types of combat or simply because they are a 'high skill' character and I simply haven't gotten good enough with them yet.
Had you asked me about a "worst character" immediately after I unlocked Captain Squawk I would have put him up there. Captain Squawk has been pushed deep into the role of sniper by the developers and they've made high skill with him a must with how incredibly slow his sights focus when you enter sniper mode. The first couple of hours with him were really frustrating until I figured out that he's best suited for long-to-extreme range sniping with a heavy dose of patient target selection- after that my goal became seeking high vanquish streaks and just ensuring that my K/D ratio was heavily in my favor.
Some characters can be decently effective doing almost anything but when you have a variant which is really pigeonholed into a certain niche or which requires a high level of skill then playing that character becomes a frustrating grind instead of an enjoyable experience. Both Tank Commander and Captain Squawk are like that.
With Tank Commander you're unlikely to be the one sitting on the "Most Vanquished" pedestal at the end of the game and if they's your standard of "good" or "bad" then you're viewing the character the wrong way. Having your Tank Commander up on the "Most Assists" pedestal should be your goal instead and you may find that you have more fun when you play towards that instead.