Everyone knows the basic core of monsters (if you don't then open the spoilers), but now Mermails have access to Tidal, elemental dragon of cascades. This card is basically a free level 7 water monsters every turn, allowing you to bring out rank 7 monsters with greater ease than any deck other than elemental dragons. Furthermore, Tidal and his baby version let you discard atlantean monsters and Abyssgunde as costs, allowing you to use their effects. Tidal can manipulate the graveyard to amazing levels, as it can drop 3 cards in the grave or get rid of 1, 2, or 3 monsters from the graveyard depending on if its in your hand or in the grave itself. This level of manipulation lets you summon Moulinglacia with even greater ease, and of course, Moulinglacia is still searchable via Dragoons. Lastly, mermails got a boost through the release of mecha phantom beast dragosack, and with Cascades they become amazing at spamming rank 7s, though not as well as Elemental Dragons.
In my opnion mono-mermails are still a better choice than Genex mermails, even though ophion is a pain. If you go first you can summon Abyssgaois with some degree of ease, and I'd rather run 3 breakthrough skill to deal with ophion and LaDD. Also, heavy infantry deals with ophion and because you run 3 you could likely drop it with Abysspike or Abyssturge, both of which are searchable via linde which is searchable via sphere. Lastly, you can summon Deepsea diva (also searchable via dragoons) and get out heavy Infantry, allowing you to xyz into armor Kappa (currently ocg only), which is a water monster with a detatch cost, allowing you to pop Ophion or any other trouble cards.
Also, Abyssgaois hurts elemental dragons immensely, since they need two outs to it in a turn. Once you deplete their resources (which seems like never, but it happens) Abyss Dweller is also really good against them. You can also side in a single treeborn frog and drop it with Tidal to stop LaDD. Prophecy is a problem however, but I wouldnt call it a bad match-up.
So, thoughts on Mermails? I feel like they are still a force in the meta and with the ability rank 7 toolbox and get rid of whatever your opponent has on the field. They may not be dominant, but they are certainly still viable.
Edited by ck49, 15 May 2013 - 10:25 PM.