A deadlock in the house is much less likely then a Johnson presidency. Right now the republicans have a majority of congresspeople from 32 of the states. A deadlock is very unlikely unless the democrats take or tie the republicans in seven of those. That would require democrats picking up a large number of congressional seats across the country. Looking at this (
http://www.270towin.com/2016-house-election/) I'd say the easiest path would be...
Nevada 3rd or 4th (winning either of these two democratic leaning races would get them to a tie)
Iowa 1st (tossup race gets them to a tie)
Colorado 4th (tossup race gets them to a majority)
Wisconsin 8th (tossup race gets them to a tie)
Arizona 2nd (republican leaning race gets them to a majority)
Michigan 1st and 7th (winning this tossup race and republican leaning race would get them to a tie)
Montana (safe republican seat gets them to a majority)
What this basically boils down to is democrats would need to run the tables, winning all over the country in places where they should be the underdogs. This would require a democratic wave year. And if there is a democratic wave year, Clinton is going to easily win 270 electoral college votes unless she is found in bed with a live boy and a dead girl and they both turn out to be Goldman Sachs lobbyists who worked in Benghazi.
The Johnson presidency on the other hand does require three unlikely things. One is that neither Clinton nor Trump wins. 538 has the current odds of that at .4% in the polls only forecast. Two is that Johnson gets an electoral vote. The odds of that are 3.5%. Both of those happening might seem like a long shot but keep in mind that a deadlock will probably only happen because Johnson is winning votes. So these aren't independent probabilities, they intersect a lot, probably something like .3% of the time. Finally the third is that Johnson can convince house republicans that he is a better choice then Trump. That might seem unlikely but keep in mind that we are talking about a conditional probability predicated on Johnson suddenly catching on fire and being really popular. So all that happening is really unlikely but I'd still say more then 1 in 1000...