I am happy almost every time I see Grum on the other side of the battlefield. He is so slow, with 1 speed I have almost never experienced him hitting any of my monsters and even if his speed is increased a bit he is still a very easy stun target.
An example:
https://splinterlands.com/?p=battle&id=sl_7bacf39ea5e554b2dee23d47d1d45156&ref=truls
When you use 11 mana on a monster it has to be more than a huge speed bump.
I have tried to play him with Kitty and it makes him much better, but he is still a perfect stun target.
When you have the reverse speed ruleset he is amazing of course, but there are many cards that are great in one ruleset.
From a brawl battle:
https://splinterlands.com?p=battle&id=sm_vfQn76DmQRy1lUAth6DQ&ref=truls