I don't know if anybody has done statistics for mutated creature stats, but my wild guess would be that its something similar to what fate-egg would give, and 10men did stats for that and the average attack of a fate-creature was somewhere between 3 and 4.
If that stands true for mutated creatures as well, that would mean your deck has a slow and expensive way of producing weak attack -- not really competitive, especially in PVP2, where you can have really fast rushes with cheap but heavier hitting creatures, such as upped recluses, frogs, graboids etc.