Was Eru or the Valar clueless?

[Angry Hill Troll]

Clueless?

Eru: Never
Valar: On several occasions, but not that often

On the question of why Faramir and Boromir both had the dream if only one of them was going to go to Imladris, recall that when Frodo and Faramir meet in Ithilien, it turns out to be very important that Faramir had had that dream:

'Are the riddling words known to you that Boromir brought to Rivendell?' Frodo replied.

Seek for the Sword that was Broken.
In Imladris it Dwells.

'The words are known indeed,' said Faramir in astonishment. 'It is some token of your truth that you also know them.'

This is a key moment in Frodo and Sam's efforts to convince Faramir that they are not enemies. If Faramir had not had the dream, one can imagine that things might have ended much worse. So the reason for Faramir to have had the dream was probably not so that he would go to Imladris.

It isn't clear how things would have gone with the Fellowship if Faramir, rather than Boromir had been sent to Rivendell. But it's pretty clear that Faramir, rather than Boromir, is the brother you would want the hobbits to meet in Ithilien.

There is a thread called "Was Boromir a mistake?" which discusses the issue of which of Denethor's sons should have been sent to Rivendell.