Kills ain't exactly hard to come by in CoD, thus, my disapproval of Hardline stems from this. Sure, UAV only Hardline has a place in srsly srs clan matches where people actually communicate and have a strategy laid out prior to a match, but that doesn't mean it's half as viable in your standard play with randoms.
Hardline's only two uses are to focus on killstreaks or speed up Specialist; I suppose the former does have viability, but it's hardly the best option one could go for. Hardline ain't gonna save your ass from an explosive so your Assault streak continues on, nor is it a replacement for Assassin. As you know, since you were once an Assassin whore. :P