I don't think that it matters which tank is the 'lifesteal tank'. What matters is that each job provides a distinct gameplay experience without giving any one job a significant advantage over the alternatives.

I think if the dev team were creating FFXIV as a new MMORPG now, with our current job selection, DRK would probably be the most sensible choice for a lifesteal/HP manipulation tank. But it makes much less sense now to revise both DRK and WAR to get there, than it does to simply push WAR further along in that same direction. It's not that big a deal.

I do want to see the tank jobs commit more clearly to a central theme or mechanic. If you're going to have a dedicated lifesteal tank, build the entire job around it. You don't need any %DR cooldowns. You don't need any barrier shields. All these effects can be achieved through temporary HP.

Likewise, you could just as easily create a job around barriers and punishing enemies for attacking them. Zarya is a great concept. Enemies hit your barriers, you hit back harder and faster.

What I dislike is when the concepts get diluted. What's even worse is when another job gains access to your unique job flavour, while keeping their own unique identity.

Everyone has a token barrier shield, even if it makes no sense for them to be able to generate one. Everyone uses the same stock of %DR cooldowns. There can be different ways of achieving the same effect. You just need to commit to deliberately going in different directions with each job, and respect each job's design space. No, you can't have Cover. No, you can't have TBN. No, you can't have NF.

The problem is that the development team doesn't really know what each job's identity is, so they don't know how to put their feet down.