A quick note, there is nothing wrong with having multiple melee characters in a group. The game has 3 options for strength based melee characters, sword and board (shield), two-handed weapons and dual weapon (single handed weapon in both hands). While there is some overlap in the skills, not all warfare skills fit all three of the builds. As an inquisitor is set up two-handed weapons at the start and fighters are sword and board, the skills that are most useful will be slightly different with each. For example, for the fighter, Bouncing Shield throw is highly effective for damage. For the inquistor, two handed weapons have a longer reach, so Whirlwind will be more effective at hitter more opponents. Beyond this, the figher has Geomancy and starts with Fossil Strike, which is a highly effect early game CC (Crowd Control) skill. Also, with the shield, the fighter should not be taking a lot of damage. The inquisitor with a two-handed weapon should be swinging for the fences, basically the goal is to accept you will take some damage, but know that because you hit much harder so you can kill your opponent before they kill you. Necromancy aides this is two ways. First, passively, each point in necromancy will give you effectively 5% life steal. That is all your damage will give 5% of that damage back to your health. Also, Necromacy should start you out with Mosquito Swarm which will directly give you health back.
The point is, that even though you are starting with two melee focus characters, the play style for each is quite different. You may find you enjoy playing both.