Tahm Kench JG Opinions (high ELO Silver 4+ only please)

What would it take for him to be viable jungle? His clear's a little slow early and he gets quite low but it becomes fine after the first back. He's pretty vulnerable to counterjungling though. His dueling is excellent but his teamfighting 5v5 is pretty weak since he's all single target. Overall, he seems to scale about average but my main issue with him is ganking early. I'm often at 75% HP or so from clearing and more importantly, I have no gap closer until 6. I can't even get into Blue Smite range many times. I literally walk to them from a bush or behind and they just take a few steps away like I'm a joke. With other junglers I played, like Mundo I move much faster just due to base MS. Is this a legitimate issue or am I playing his ganks badly? Is there anyone who even mains him as JG in top tier play? I love his personality and kit but I also don't want to handicap myself or my team.