I have a grow tent for veg and bloom, and I use my bathroom for a cloning station. I have no cabinets so I hung a cord with 3 CFLs over a small stand supporting my humidity dome. I've had zero and 100% survive. My problem was always over watering. So now I am strict. Rock wool is best. but Jiffy pellets are cheap and easy to find. So, first I soak the pellets in water. I might mix a very light solution of B1 (Superthrive 1 drop/gal) and H2O2 (hydrogen peroxide 50-100ml/gal), but plain filtered, oxygenated water is fine. Then I take my cutting, clip the leaves, score up the stem and dip it in hormone. I like the gel but again the powder is easy to find. Then I put the stem into the Jiffy pellet and I am careful to not squeeze it much beyond setting the stem because I want it to be most arable and not compacted. Rather, I place the pellet on several folded up paper towels in order to soak up the extra water. When the pellet looks wet but no longer saturated, I put it into a humidity dome. I wish I had a small heating pad under the bottom to warm it a bit, but I don't. When I did, it all worked a bit better. After this, I never mess with it at all. I just take the top off the dome when I shower to give it air and humid mist. I place the dome back when the room is still foggy. Also, at first I use 1 23w bulb, then after a few days I add another and then the third. Temp is mid 80's and as long as there's condensation inside the dome, you have good humidity. It takes between 1 and 3 weeks to get roots. They will all survive if I am strict with myself. But if I water them, especially if I water the pellets themselves, the stems will turn to mush and the clones will all die. Another thing I learned from my own faults is to not mess with them too much. It takes time for the humidity to go back up after lifting the lid, so leave them alone and their environment will stay stable and healthy. If it seems too dry and you want to add moisture, mist it around the interior black area of the dome bottom and not directly onto the jiffy pellets. Let them absorb excess water from the environment rather than shed excess from within.
I hope this helps.