@Naoki Yoshida-> Make Samurai a Tank class!

[Shippuu]

Hmm, is it really just that ? In that case these statistics aren't really useful.
I still think you can say the tank population increased, if more people bothered to level a tank to 60 it seems logicial some of those people would start playing it.

The overall statistic of Tank/DPS/Healer from the recent census didn't take into account the levels, so the 2% increase was tanks as a whole at 21%.

The later chart showing only level 60's showed tanks as 23% of Level 60's. So the level 60 tank % is higher than the overall tank %. It's still a good thing even if only existing tank players simply leveled DRK, that's still a large number of people revitalizing leveling content.

Probably not the sole purpose but look at it this way : DRK is a huge success, it's the most played tank and the tank population has probably increased going with what we have.
Even if some tank mains switched jobs with it's release (me included), I seriously doubt every DRK player played a tank before or would have kept playing tank were it not added.
Personally DRK is pretty much the sole reason I got back into the game, I got sick of my PLD even with the few new interesting spells they added in HW and I didn't want to play it at all when I came back some time ago. DRK looked cool and interesting, I leveled it and here I am.

It's definitely a success, DRK is the most played tank despite not actually being the best tank in the game which is very telling. One would expect Warrior to be the most played given it's reputation as clearly being the best Tank, but DRK is higher.

We have to also take into consideration that DRK could have acted as a "gateway tank". Even if someone tried DRK and didn't like DRK specifically, it at least exposed them to tanking and some may have then gone on to try the other tanks and potentially taken them to level 60 as well. Without literally polling a mass amount of players there's no way to get accurate data on if this was the case and by how much unfortunately.

[StarRosie]

We have to also take into consideration that DRK could have acted as a "gateway tank". Even if someone tried DRK and didn't like DRK specifically, it at least exposed them to tanking and some may have then gone on to try the other tanks and potentially taken them to level 60 as well.

I can agree with this, DRK having the benefits of starting at lvl 30 instead of lvl 1 definitely gives it the ability to let people dip their toe into tanking to find out if it is for them or not, without having to invest a lot of time into leveling and gearing for the dungeons.