It makes just as much sense to tell people that don't want speedruns to use PF as it does to tell people that want speedruns to use PF. Using DF in either case, players risk being grouped with others with a different play-style. Some people are good about adapting to this (tanks will go slower or others will go faster, for example), but some people don't want to adapt.

It doesn't matter whether people want to speedrun, not speedrun, adapt, or not adapt, these are just play-style differences and it doesn't automatically make someone a jerk because they have a different play-style than yours. I don't understand why so many people want to penalize the latter people even if the penalties also hit some of the former. Besides, as I have been saying, there are other ways of dealing with people leaving an instance right off than a penalty timer (like their losing their roulette bonus).

Penalty timers prevent players from playing the majority of the game (since the majority is instanced) and I don't think it makes sense from a business standpoint to discourage players from playing your game for chunks of time. Not only that, but it's questionable how much penalty timers even do the job they're intended to do. I would absolutely still leave right away, even as a DPS, if I got some impression that I was in for a miserable experience (which almost never happens btw). As a sidenote, I think DPS queues are really overestimated; I switched from main tank to main DPS at HW release and my queues have been 5-10 min longer AT MOST.

As for people asking for votekick, I have never had that happen in the first 5 min of a dungeon, ever. If someone asks 20 min in to be vote kicked, they probably aren't asking because they don't like the duty. I know it all comes down to personal preference, but I'd kick someone if they didn't at any time want to be there. Then I'd just ask someone from my FC or LS if they could join in progress to help me out. Building connections with other people seems like a better solution to me for dealing with people who leave or want to leave a duty than resorting to penalty timers.