I haven’t heard it as much as he seems to have, I must say. But I do recognize the usage, especially where I live, in Holyhead, where a lot of Irish people live, and many more pass through the port. It’s long been a usage in Irish English - and also in the Caribbean - where it’s heard in statements as well as questions:
An Irish example: ‘It’s the greatest fun at all.’ (i.e. it’s wholly the greatest fun)
An American example: ‘Use one statement at all.’ (i.e. only one statement)
OED has citations of this use from 1375.
The usage in negative constructions also has a similarly long history, as in no problem at all and he can’t dance at all, where it means ‘to any degree’. These have entered standard English. And the same point applies to the earliest interrogative use, where the phrase has a range of meanings, such as ‘in any way’ or ‘for any reason’. First citation here is 1566.
Did you go there at all?
Why should people care about football at all?
The usage which my correspondent has noticed developed out of this. Here the phrase is used to modify the question, and has the sense of ‘in any event’ or ‘indeed’. From a pragmatic point of view, we might gloss it as ‘may I ask? or ‘would you say?’. It softens the force of the question. It might have something to do with lack of confidence, as my correspondent thinks, but more likely it will be functioning as a politeness marker. Here are some OED examples (the first one is from James Joyce, in Dubliners):
Is he a priest at all?
Can we see him at all?
And - to my mind the most fascinating one of all - the reduplicated usage:
How is he, at all at all?
I take this to be a selection of two of the range of meanings expressed by the form, for emphasis: ‘How is he indeed, may I ask?’. I think I’ve even heard it used three times, but I can’t remember where.
I don’t know if the usage is increasing among people who don’t have an Irish or Caribbean background, but I wouldn’t be surprised, given the popularity of TV series in which Irish speech has been prominent, such as Father Ted.