A DPS-spec'd Juggernaut has far worse CDs than a Marauder. A *tank* Juggy has great CDs.
They can taunt to assist with certain mechanics, and they are a solidly "tier 2" DPS (along with Snipers, Mercenaries, and (really good) Assassins). There's no reason not to take a competent one other than having an equally competent Marauder or PT available or a bunch of other melees already, as content with too many melees tends to get overly complicated.
Snipers are not "tier 2" DPS classes.. They're "tier 1". I'm curious to know how you were able to say Snipers are 2nd grade in terms DPS in the current PvE content..