It's very clear that General Grievous played a vital role for the Separatists during the Clone Wars, especially after the death of Count Dooku during the events of Revenge of the Sith. He was important enough that the Jedi Council thought that they could bring a swift end to the war if they were to kill or capture him. Mace Windu even said:
Then the Jedi Council will make finding Grievous our highest priority.
It's also no secret (to anyone) that General Grievous is an extremely skilled swordsman, having engaged and killed numerous Jedi in lightsaber combat, and he isn't even Force-sensitive. In one early fight (and arguably his best fight), Grievous fought four experienced Jedi Masters and a Jedi Knight all at once, killing or seriously injuring all except for one of them (and he primarily relied on only two lightsabers in that fight, only resorting to three blades by utilizing his foot). So, given the fact that Grievous is a high-value target, and considering how dangerous he is even to some of the most experienced Jedi, why did the Council decide to only send ONE Jedi Master to Utapau to stop him during Revenge of the Sith? I can understand them not sending Anakin, but I see no reason why Obi-Wan should go alone, regardless of how reliable their intel was.
Granted, Obi-Wan is also a skilled swordsman who has managed to survive at least a few one-on-one fights against Grievous, such as these two examples, but the same can be said for Ki-Adi-Mundi. Even if you want to argue that Mundi was too busy to help Obi-Wan, Mace Windu didn't appear to be occupied at the time, and the same is true for several other Jedi Masters, such as Kit Fisto, Agen Kolar, or Saesee Tiin (who all took part in the unsuccessful attempted arrest of Supreme Chancellor Palpatine). The point is, I just don't see the logic in not sending a team to find Grievous.