Guldo is a very interesting unit, he can stun, lower the enemy's ATK and DEF and doesn't need a full Ki meter to Super Attack.
Guldo is a TEQ type and his mechanics would actually function very well on his mono team, Extreme TEQ: anything that can limit the amount of attacks or damage directed towards the leader of the team, [Mythic Evolution] SS3 Broly, can be considered a nice addition, and lowering the enemy's ATK can also allow [Merciless Condemnation] Goku Black (SS Rose) & Zamasu to tank even better as they build up their ATK.
So where does this unit fall? Just like the other members of the "Ginyu Force", Guldo has very specific links that limit his usage: the only saving grace would be "Brutal Beatdown", but even this link is not that common.
Should you use Guldo on your team? His main usage, aside from the stat lowering mechanic, would be to stun the enemy and we already know that on the latest events the Bosses are immune to that.
On Super Battle Road Guldo suffers from competition with [Absolute Suppression] Turles, who also has a form of self-sufficiency in his Passive, tanks better and has better links: the only reason to run Guldo would be the fact that his chance to stun at 100% in the Potential System, with a heavy focus on Additionals, is going to be higher than Turles'.