I tried working with that skill couple of times. If the skill is not close to 90%-95%, it gives you one of the following two messages from the NPCs:
- Ask someone who can be able to help you
- I cannot do it right now, maybe later

When I mastered it and asked almost all Guildguards/Guildmasters/Healers or any goodie NPC, I got something out of it. The message seems to be like you failed in your supp.

The IMMs may say that may not be the mechanics of Beseech. From RP prespective, I have considered Beseech is like begging for few pieces of copper. Like panhandle on thiefs.