I completely disagree. Yes Tigress, Icicle dont bring much to the table but Brainwave soloed the JSA in print many times.
In his retconned debut he soloed and took out the JSA on his own in All Star Squadron. Prior to engaging them he met the team and gave Spectre a TP push to go fight something else because "he wasnt quite ready to deal with him" he then took down the main team of the All Stars as well and was only stopped by Alan Scot going all out.
His earliest appearance in All Star he pretty much faced a line up that included Fate and Spectre and did well without aid.
In All Star 55 he also took onnthe entire JSA on his own including all in the line up from the premier plus Fate, Alan, PG. He separated them and fought them with his illusions all over the globe. He took out Fate and Alan with onenin South Africa IIRC and they were saved by Robin.
There were a few stories where he handled Alan alone.
There was also a period in the SA where the wizard led the injustice society and on his own was taking on the power houses. During that time he had a crystal he wore around his neck and had given up the top hat etc for a green cloak.
Grundy has also soloed Fate + Alan + Hourman since his body absorbs magic and was amped by it o. Showcase 55