Sure the walrus is like a tank on land but the movement handicaps are pretty redic. Any half competant noob should have no problem walking away from it if they need to run and if the shifter wants to shift back and forth between walrus and other forms then that also give you plenty of extra time to get away and drains mana and forces them to recast spells. All in all if you let a walrus sit there its nasty but its your own fault then for not exploiting its mobility weakness.