riven and fiora kled rhaast arent juggernauts they are fighters. they thrive from sustained combat or at least can get in quicker (lighter version than juggernauts).
the big beefy guys are called juggernauts that your click box pretty much hovers over due to their iron potion and yes chogath is a mage juggernaut specialist that can go ad/tank if he wanted too same with nasus.
the 250 (riven) range each use is a fighter type AD skill (played a mmorpg game) its a fighter/assassin skill due to it being on a cool down dependent champ if she is on cooldown after her whole 'burst' she still has her passive (sheenlike autos) which is the fighter part of her so she uses her basic AD till the cooldowns are done then she can burst again after.
darius is a bruiser due to him actually being beefy (large hit box) . lets say darius (no skillset) and riven (without her skillset) attacked each other and for funzies riven has her sheen like autos charged already darius would still win by default due to his inflated base stats and passive thats the reason why hes called a bruiser hes allowed to take a punch in the face riven (early game) cant if she doesnt retreat.
the only reason why bruisers appear stronger than others is the access to defensive items and movespeed buffs yet deal damage due to some condition in their champ that amplifies damage.
now lets compare rhaast/renekton to shall we they both have easy to access sustain both have cool down dependancy that can stay in lane longer also bursty in nature so again they are fighters that have no natural kill condition like juggernauts do. but they can depend on their AD if they wish to do a fist fight but heres the problem the enemy has attacks that can gib you if your not durable enough which is why sometimes the "kayn" player phases away just for a second to heal/cooldown manage and repeat he has 3 chances to kill a enemy after that hes a sitting duck autoing a person
. rektion has AOE DOT on his person which amplifies a sunfire cape like effect which is a fighter thing not a assassin thing it hurts the enemy while giving you extra hp but not instantly gibbing them on the spot. (garen q e ulti true damage also)
now rektions playstyle is more hit and run fighter playstyle 'dive in stun heal up Q spin (fury) get out e'. after that he can only auto and ult to survive.
urgot is a reload playstyle that revolves you getting into his kill condition (active shotguns and execute marker ult) thats a juggernaut he can only slow you and his only power mainly is in his passive that he has no control over except maybe his rear shots by default honestly i think riven can fist fight him (full passive on riven) due to this weakness/strength. benefit urgot has late game he can pretty much reload instantly after his shots are used up.
ask anyone here ill wait. i dont mean a close friend either. someone who knows a pros/cons that knows that juggernauts can/cannot fall off conditions.