1. Dry your tobacco much more
2. Experiment with packing. Packing tight is a mistake, packing too loose is also a mistake.
3. Try a briar or a Meerschaum. Cobs have wooden parts inside which char and burn, and the taste is nasty At least that is what put me off Cobs
MM cobs do have a vegetal taste for the first couple of bowls then there's the protruding stem that gives off a wood taste when one gets down to the last bit off the bowl.
Here's what I do with a new cob.
The first couple of bowls I'll ensure that the tobacco is dry, not moist.
Once I taste the hard wood stem, I remove any ash, then add a few pinches of tobacco & really fire it up to get the protruding stem smouldering. This will not interfere with the integrity of the fit of the stem.
Do this 2-3 times & no more issue with the protruding stem, no more woody taste.
There's a little bit off space between the bottom of the bowl to under the draught hole. By using a dry tobacco, when at the end of the bowl, tamp down the grey ash to build cake until it's almost touching the draught hole.
Then one just needs to be a touch careful not to disturb that cake by scraping too deep.
I've got some really nice briars that are great smokers. My 3 MM cobs smoke just as well. In actual fact, some blends taste better in a cob.
They're great pipes once they've been 'broken in'.
This year I'll be adding 3 more MM cobs to my rotation. They are so worth the initial effort.