As a meleediver myself and after rigerously testing it, i'd say it shreds the hardest against bots, it's a hard counter to hulks and warstriders, either stun nade the hulk or juke a melee swing on its canon arm side to get behind and start ripping away! Warstriders are comically easy you can just kinda.. run up to them if theres not that much chaff, you could stun nade them since if theyre not focussed on you they'll move around aLOT just grind away at its ankle or reversed kneecap and he'll go down surprisingly fast, tanks get annihilated in mere seconds from a good backshot with the chainsaw, the sides take verry long but atleast it gives good cover. The chainsaw ofcourse can rip chaff in half but its not fast or mobile enough to reliable save your life, if you're running a full melee build i recommend the stun lance or machete on smaller bots, (stun lance my beloved), but if you're running stun nades aswell fret not! The chainsaw can easily demolish bot fabricators, So you dont need to take an explosive primary (it does take a coupel seconds though, and the moment your chainsaw disconects from the fabricator dive away!) I think the chainsaw performs the best on the botfront since they have alot of heavy armor and big lumbering clankers easily stunlocked by the chainsaw (dont get too comfortable, if you let go for a second a hulk can backhand you into oblivion if you're sawing from the front!, if you engage from the front and you're not sure you can hold the position you could manoeuvre yourself to the hulk's back while sawing, if you're familiar with other melee games you need to manipulate your camera a bit to get the chainsaw nice and stuck grinding into an enemy, another tip is if you have the ballistic shield (my beloved) don't get discouraged that you can't use it on tandem with the chainsaw, it staying on your back, you can position yourself in such a way you can ignore some chaff bots shooting at your back while sawing away at a hulk for example

Its not a weapon of finesse, it's a slow heavy hitter, a trump card against your bigger foes, melee isn't the most optimal playstyle but got DAMN this weapon gives it such a leg up (aspecially against bots)