Bellini would have been certainly shocked listening to Del Monaco singing the role!.
His preferred tenor, Giovanni Battista Rubini, creator of Arturo or Elvino, was not available for the premiere of "Norma" at La Scala, in 1831, and he had to deal with Domenico Donzelli, a more limited in coloratura performer and the owner of baritonal-like voice, that was singing in full voice up to the high G, and then, using 'falsettone' was able to sing up to a high C (sometimes; in
Meco all'altar di Venere, Bellini tried to use the capabilities of Donzelli, but he marked the high C as optional, nevertheless

).
Bellini had in mind to rewrite the score for Rubini eventually, but he died before he could do that (incidentally, Rubini sang nevertheless the role with Bellini already dead, at Paris's Théâtre des Italiens, and with great success).
In my view, it's a misread to think of Pollione as a strong, virile character. He is not that, either in the plot, or in the score. He is not Julius Caesar conquering the Gauls, he is just a provincial governor having an affair with two local ladies, and soon to be replaced by a 'più temuto e fiero latino condottiero'.
Looking at the music written by Bellini, the only real "heroic" part is the cabaletta
Me protegge, me difende when Pollione is promising to defeat and punish the Gauls... a totally vain threat, as we can see later; instead of conquering the Gauls, they are capturing him marauding alone, and he submits weekly to them, and later to Norma, going to the bonfire by her hand. In the meanwhile, he had a lovely duet with Adalgisa, that is anything but "heroic", and must be sung accordingly.
Singing this character thinking that he is Julius Caesar (or, one could think sometimes, Attila) is not the best way to portray the role that Bellini wrote.
My favorite Pollione on record is Carlo Bergonzi. His voice was certainly close to what we know about Donzelli's, but, more importantly, he was reading the score and the character.
p.d.: Good choice about Festus, anyway.