I can’t beat the 3 leviathans they are getting crazy Bonus Actions like each one gets 4 in a row and they wipe out my whole team. What level are they? 80? and they aren’t even S rank. My team ranges from 50 to 70.
And also I have a Glazio and a Soltusk should I fuse them to make a Dreadwolf or not?
hmm although Dreadwolf lacks 1 hit moves I would fuse it just because I like wolves 
Looks great and has better AOEs
True that
There are a number of ways to combat the leviathans, the first and foremost being the stunners
The second would be just level up every guy on your team as much as possible and beating face
It took me a long time to beat them without using stunners but the feeling of accomplishment behind it is huge
Voted yes, Dreadwolf is a very good ark for PVE.
A good Air Arkadian will do much better for you against the Leviathans though.