I do not know anything about Roman history, so these are really my two cents.
First of all, life and, above all, death in ancient times were surely much more grisly than nowadays. In war, people had to stub a sword in somebody's else guts and rotate it so as to inflict maximum damage to his internal organs. Common injuries were chopped hands, or legs, with resulted in death by gangrene in a few day. Not a nice way to die.
So, crucifixion, was designed to be an horrible and tortuous way to die, much bloodier and gorier with respect even to those standards. I always say that crucifixion was not being condemned to death, but being condemned to be tortured to death.
Moreover, If we refer to the only detailed account of crucifixion that we have, it seems to me that it was carried out with sadistic pleasure. I mean, the mob shouting "crucify" could just have stayed silent or asked for all the criminals to be released. But they wanted to see a man put to a bloody cruel death. When the soldiers used the crown of thorns, or spitted, they did it out because they hated the victim and wanted to enjoy their sadistic pleasure by inflicting torture and abuse.
This is not surprising to me. Sometimes men who, taken singularly, would behave perfectly well, when instead are in particular situations and/or groups. take the worst out of them. They let themselves go to their lowest instincts, sure that they will get away with it.
When having a girl in their hands, well, I get shivers at what they could do with her. There are reports from the second world war, where group rapes and killing of the girls in conquered villages where just considered as "rites of initiation" for the younger recruits.
Of course, during hundreds of years there could people carrying out the job of crucifying a guy or a girl just as an unpleasant task, to be carried out in a detached and professional manner. But I tend to say that, given the intention of the crucifixion itself, to a be hideous and spectatularized way to put people to death, and the nature of men in these situation, that a great amount of them has been carried out with additional sadistic tortures to the victim, just for the pleasure of doing it.