[PvK]

Look more closely at Early Oceanian units - there are two other types of troops who can go on land who are both better than Mermen, and who are complemented by them when mixed with a few Mermen. Put the Turtle Warriors in their own squads and order them to Fire Closest. You can also Summon Kydnides and they mix well with heavy Oceanian troops and they are very strong (but you have to decide how much water magic you want to spend on them).

PvK