Before the update came I had planned to move it up to S tier, so near enough 
Being slow is the biggest problem it has. However, the moveset is actually pretty good aggression now and I think the entrance creating two Goldoids is more useful than people would give credit. Lower tier monsters tend to have more situational attacks, but since this latest update there are many more with good movesets… Rhinedragon will inevitably slowly drop in the tier list.
Don’t worry, got you covered there 
The way they’re working now is very hard to grasp, because I’m used to years of them being so good. I’ve always felt the sleep is the strongest part of the entrance, but the stun was very useful too. Malwing’s main move is blowback, which still has no problem. Reckless timestrike was more for stun absorbers or monsters on low HP (then it’s a 70TU way to charge bloodcrave). I don’t feel like that’s got much worse either. Malwing also adapts better to mythics (tanky monsters) whereas Sobeking struggles a bit more.
Overall, I thought I’d leave them at S+ for now but probably drop them both to S tier quite soon. I think they’re still both very good compared to a lot of legendaries.