Are they trying to encourage Vladimir to build tanky? (or at least tankier than he builds currently)

First, his passive has been changed. He gains less HP from building AP, but more AP from building HP. This encourages building more HP items and makes going full AP a little less optimal since he will be squishier late game.

Second, his Q's base damage has been lowered, but now after casting it twice the base damage is doubled and the scaling is doubled too. Not only that but it will heal for a percentage of Vladimir's missing health (has synergy with more HP heavy builds)

His E now scales with HP. Not only that, but it slows when fully charged. Generally, tanks and bruisers have an ability that scale with a defensive stat and has CC; and that's exactly what Vladimir's E has became now.

His ult now heals Vladimir even more.

For me it seems obvious that Riot is trying to make Vladimir build more like a bruiser (albeit an AP bruiser) instead of a mage.