I'll give you some tips as a frequent Rakan player:
Unlike any other dash in the game (afaik) , Roots will stop Rakan from completing his W. Not only will he be cut short, but the knock up won't happen. This means if he using the max distance of W, you have he most opportunity to stop it. BUT, if he gets to the location, the knock up will happen regardless of CC.
This means I find it annoying to play against
, both popular supports nowadays because if they see me get close, they can easily root me. I cannot even abuse the cooldown of this and try later because the W CD is like 15 seconds, while Lux and Zyra CDs are around 10.
Rakan also has hard counters. These are the most annoying champs to play against as Rakan:

among others that I am probably forgetting.
All of these champs have some way of grounding Rakan, have a dash that they can use to avoid the W, or have an easy way to interrupting the dash.
This Ult + W + E has really good synergy, yes. But, I will tell you that after Rakan does that combo, he doesn't do anything else. On the average engage, I get two, maybe three people in the ult + W combo. That is pretty good, but there are 2 or 3 others on the team. So, I have a choice: do I try to tap the other champions, who are clearly scattering when they see the combo, or do I go back to my team with E? The problem with continuing is that I'm most likely being focused from being literally in the middle of the enemy team, so I may not survive tagging the other two. BUT, if I go back to the team, my contribution ends because I have no ult, my W is on CD for another 7 secs (by that time, the fight is done) and all I have left is my q which does not do much damage. As a Rakan player, I ult in, E out, and hope the team does something. If not, I'm dead.
In lane, Rakan is actually not that tanky. He has a shield with a CD of 40-30 seconds in lane which is long. His base HP is also very, very low. Lower than other supports like
etc. abuse this.
Are the PBE nerfs justified? Sure. But here are some tips to help you out if you are frustrated.