Nothing's wrong with the change, but The Darkness II doesn't offer any kind of substantial variety with enemy layout, positioning, etc.. (playstationlifestyle.net)
The only real drawback to Raid Mode is that it features all the same content as the main campaign besides enemy layout. (videochums.com)
Items have actual value (even if the amount of crap that has to be picked up to receive that value has massively inflated) and enemy encounters are more unique (nobody respawns until events introduce new enemy layouts) and way more engaging. (gonintendo.com)