They've skipped at least three major battles. Green Fork (where Tyrion gets knocked out and the Lannisters defeat part of Starks army), Whispering Wood (where Jamie Lannister is defeated and captured by Robb Stark) and the siege and sack of Meereen (was very bloody and hard fought in the book, in the show Dany just sneaks in a couple unsullied and the town falls by morning

)
The only major battle they showed was Blackwater, which was a kick ass episode. They need to do that with every major battle.