We usually have MORE combat on the East side of the board! Stark and Martell gang up on Baratheon, or Baratheon and Tyrell gang up on Martell.
Who is trying to "get around" whom?
I have to say, I've not played as many games with Martell as usually my group only goes up to 4 or 5 players, its not so bad when they're involved.
What I mean is lets say Baratheon wants to attack Stark, its literally Stark ship numbers vs. Baratheon ship numbers (usually 3 vs 3) and so the only factor in combat is House Cards and fiefdoms (compared to land combat where there can be 3 or 4 support orders involved, varying strength pieces, etc.). Unless casualties are inflicted Stark will simply retreat into his Port/north sea area and then attack him back the next turn. I've found in my games that on that side of the map people would rather not risk losing for fear of having their navy wiped out or wasting useful House Cards, so they all either support or raid.
Things are slightly more elegant on the Western side where three areas can all interact in one combat. In a sense, if Tyrell or Lannister wanted to invade the North, they can (attempt to) bypass Greyjoy. The same is not true of the East. Does that make sense..? I'm interested in a way to make ship combat feel more dynamic and less predictable.