He's kind of left in the dust, and countered by every meta top laner. He's actually forced into the jungle, part of the reason is to avoid all those bad top lane match ups. According to http://champion.gg/champion/Rumble/Top, his "best" match up is Malphite, which he has a 45% win rate. It's sad seeing Rumble in this kind of state.
Since I've already wrote a huge wall of text about this one, I'll just copy-paste it if you don't mind~~
As a long time Rumble player, I'd say that at this point what really holds Rumble back from being viable in the top lane is the current state of AP and MR items. As you said, duelists currently do force him out of the lane (perhaps too much given the fact that cough Rumble's supposed to be the lane bully here), and I do agree that they deal with him rather easily if he missplays.
That is, if he missplays. In the hands of a good player he can adjust to any given situation no matter the matchup, having easy time in the lane? Stay at 50 heat, harrass with Q and push the enemy away from minions. Getting poked? Come up to last hit/harrass only with W ready, space it out for enemy's poke abillities. Getting pushed out of the lane? Stay back and scrap some lasthits with E, disengage with 2x E + W whenever enemy tries to all in, ult under yourself if necessary. There's a lot of stuff he can do even in the most unfavourable of matchups.
Now my point is that currently MR items feel like they pretty much completely stop Rumble's progression at any given moment of the game, be it Maw of Malmortious, Spirit Visage, hell, even only Mercury Treads. All of them are strong enough (even when not finished) to deal with Rumble's damage and are cheap enough for enemy laner to afford them before he gets his toys. But then, even if he is ahead, his core items are much more expensive than said MR items, usually at the point Rumble has his Haunting Guise + Blasting Wand and is missing 500g for Liandry's, enemy's already covered with completed MR item of choice (or just basic component + Mercury), which completely turns the lane around and Rumble's lead becomes meaningless, unless the enemy isn't capable of all-ins, then he just gets burned to death, just takes much longer.
And now what determines the success of Rumble jungle over Rumble top is the fact that when the enemy is directly facing Rumble in lane, they simply adjust instantly and start occupying Shopkeeper's MR item section to just win the lane by clicking on the right icons in the shop, when they face Rumble in the Jungle, if he's in a teamcomp not purely made of magic damage (or gasp he's the only magic damage dealer on his team), then the enemy won't be so eager to just rush magic resistance. They'll obviously aim for some other defensive items then, since they won't face Rumble all the time, but when they do, they just get melted because of lack of mr. But then, when late game comes, Rumble jungle starts to suffer from the same weakness that pushed Rumble top out of the meta, the cost efficiency of magic resistance.
That obviously also has to do with Rumble's horrible last hitting capabillities as well (seriously though, it delays his core items way more than it should), but the point still stands true. Rumble's been hit the hardest due to MR items changes, since as you might have noticed, all of the mentioned items are purchased mainly on top laners, people who's Rumble gonna face while laning. In my eyes, all it takes to make Rumble top not fall back so much is to have another AP/MR items overhaul, leaning more towards helping the ap side, hopefully the mage update does something about it.
tl;dr In order for Rumble to come back top, Magic Resist items need to chill the fuck out
Maybe they should have thought about it better when they gutted him over and over.
