For that matter, the stated reason for the Enterprise-E’s posting makes good sense. History is full of weaker powers carving chunks off neighboring great powers that are otherwise occupied. Leaving the border with the Romulan Empire undefended would be irresponsible. The history of military warfare is also replete with cases in which maintaining a reserve force, capable of engaging at a time and place of its choosing, was able to turn the tide after one’s main force had been committed to battle and lost much of its flexibility.
As for the question of whether it’s better to have Starfleet’s most advanced ship defending the border, or perhaps a few less-capable ships - well, that’s a strategic decision best left to Starfleet Command, and I’m not qualified to second-guess it. 
The fact that Picard doesn’t understand these factors, or refuses to understand them, illustrates one of his real flaws - he’s really just not qualified for flag rank.