Cronus is an upgraded replacement to the Skana, it is easy to craft and is an overall damage boost.
Against Infested, the high slash damage is effective against them. The fact that the Cronus only strikes one target at a time may make using the weapon inefficient against the hordes the Infested tend to come in.
The listed firing rate is a speed multiplier for longswords. The real rate is 2.2 hits per second (0.45s to hit once). This is because the firing and charge rate of melee weapons often gets skewed due to attack animations.
On Update 7.8, the Cronus Blueprint was only a guaranteed reward the first time Tolstoj is completed and the chance for it to drop exponentially decreases each run afterward. This was put in place to prevent credit farming. This was then changed, as weapon drops are now obtainable by chance upon completing Assassination missions along with the Warframe component drops.
The Cronus blueprint drops as a pink orb when Vor is defeated.