Given the low number of seats/high standing capacity set-up they had, neither of the routes they were used on in West Yorkshire were really appropriate. The 4/4a was marginally more suited, being a cross-city route with few end-to-end passengers... but they were then moved (and joined by the York vehicles) to the 72 Leeds-Bradford service with great fanfare. Whilst this route also isn't really ideal for end-to-end use at least in the daytime (the X6 being faster and the train faster still) the marketing and branding seemed to suggest it was trying to capture that market (another example of First competing with themselves) which inevitably led to disappointed passengers who promptly returned to their cars.
A more appropriate use would've been as a park&ride shuttle, which surprisingly wasn't how they were used in York despite that city having invested heavily in P&R. Particularly if combined with a dedicated busway such as the Manchester Road one in Bradford. A park and ride from Odsal or the M606 might've worked but for three major issues:
Firstly, that busway is unidirectional (albeit different directions at different points) so wouldn't have been so effective at beating congestion. One option would have been to provide stops on both sides of the busway and operate it in the peak-flow direction, but that would require land-take... and then how do you handle the changeover between the peaks?
Secondly, AIUI the ftr "bodykit" prevents fitment of guidewheels, and I'm not certain the busway is even compatible with articulated buses.
Thirdly, as Bradford doesn't quite have the demand for an all-day, high-capacity park-and-ride, it'd still be a solution looking for a problem.
Like so many things with the big bus companies (FirstGroup especially and particularly under ML) the ftr was "all mouth and no trousers".
Leeds needs a genuine lightrail/tram/metro system (possibly including a Bradford line), not a bus with a fancy uniform... and it needed it 20 years ago when Manchester and Sheffield got theirs.