The problem is that with the new style, the downtime bars some times (when the player have many buffs) cover the Quick Bar. And also, some said that the new hp bar position overlap with the loot boxes bar when one roll the dice for an item.
Then i came with the idea of create a "Suggested UI" that combine both, the "Old UI" with the "New UI". To create it, i increased the size of the buff icons in a 20% (to make the downtime bars more visible)and added small downtime bars below them. Those bars are small but still let the player have a clear view of the skill downtime.
This new UI have the adventage of the old one, with the buff icons displaying in an horizontal orientation and the adventage of the new one that have an easy way to see the buff's downtime. This "Suggested UI" would also have the "+" button to let the players to switch to the old one.
Old UI

New UI

Suggested UI

I hope this can solve the problem.
Also, a suggestion for the other UI they added, the one that show the skills that were casted recently and which CD is over. Maybe make us able to click over it to recast those skills or even turn it in a mini-quick bar that we can move where we want.