is it worth fusing your dragons and making Omegawyrm

or is it better to just have them all 4 individual ?

Omegawyrm is very useful in PvP. So are Typhonwyrm and Magmawyrm, so I would recommend fusing to get Omgawyrm, as well as the two others (I believe even after you’ve fused to get Omegawyrm you still keep the other two in your PvP list). The starting four dragons not so useful, they aren’t as heavy hitting and get taken out pretty easily too.

For PvE Omegawyrm is also worth it.

Definitely go for it.