You can't really compare an offensive shifter to a warrior, a warrior does both offense and defense rather well whereas an offensive shifter just does offense, an orc would be a better comparison. A utility shifter is your equivelant to a warrior and they do just fine in PVP all the way up the ranks.
In terms of doing things solo unless you go utility it is going to be tough before you get the shapeshift skill so you can flip back and forth between forms more efficiently. This is due to the specilization of the foci, to do PvE solo you need a certain balance.
If this is your first go and you want to be rather independent in the mid ranks I suggest going utility/offense. Utility gives you the balance (honestly 3rd utility forms can beat most melee chars toe to toe without preps) and offense gives you a bit more sealing power in PvP. Between the 2 you will almost always be able to fill a role in a group.
Water shifters hero so fast because their forms tend to have a good balance of offense/defense and there are a number of good underwater ranking areas.