While I know what I'm about to recommend may not be exactly what your looking for, but you said you wanted to be good at melee and be able to tank so here is my strange suggestion.....
Dread Necromancer.
Yes, stare in shock.
A Dread Necromancer at lower levels can be one of the best melee classes in the game provided you take the right feats and skills. DN's don't rely on BAB and lots of damage to be good at melee, though. Rather, how they do melee is make creative use of class features and, feats and skills to utterly humiliate others in melee. What do I mean? If you take tomb tainted soul at 1st level, you get to be healed by negative energy. Dread Necros get a negative energy touch they can spam. Tomb-Tainted soul + Charnel touch = infinite out of battle heals. Take a lot of damage in battle? No worries, after every fight your back to full health. Not even a fighter can pull that kind of recovery. This out of battle heal alone makes you a decent tank type because while you have less HP then a fighter or some other melee class, you will be at full health at the start of basically every fight.
However, where DN's REALLY get nasty is fear effects. As you know, fear stacks. DN's get a fear aura that works wonders when combined with intimidate and a feat that I forget the name of which basically allows you to use intimidate in battle to keep fearing your opponents, or something similar. Basically, that feat plus your fear aura and a good intimidate skill will allow you to stack fear effects like crazy. So not only will you be able to enter every fight with full HP, but enemies who face you will most likely be cowering at your feet in a state of utter panic while you hack them up with the one martial weapon the DN class gives you. (For concept/flavor reasons I usually take the scythe when playing DNs, though there is lots of other good choices for martial weapons to pick up.)
Beyond this, there is the fact that your a tier 3 class with full spellcasting and at level 8 you become the best necromancer in the game who can at that point have undead hordes do all the tanking work while you use your save or dies and other such spells to take out enemies. While you said you wanted to take a melee roll, you don't have to take a tier 4 or 5 class to do that. Oh, and with the rest of the party being such opposite power wise(Druids are tier 1s and Ninjas, while I forget their tier are quite low on the totem pole) it seams like having a "balanced" tier 3 on the class would make things less of a 1 man show then if the party was say a ninja, druid and fighter.
However, in the end it's your decision on what to play and if you want to be a fighter, go right ahead, nothing is stopping you. I'me guilty of playing some "crappy" classes(I actually used a True Necromancer once..*gasp*..yes..I did just say I used a True Necromancer...) myself and I'm not ashamed because the game is all about fun, in the end, and if the fun of being a fighter or barbarian is enough to satisfy you despite the fact you will be significantly weaker then your party's druid, go right ahead. I just thought I would pose the idea to you that you don't need to play a pure melee class who's weaker then most others to actually be good at melee...
Oh, and I know that somebody would eventually do that with a cleric, but I decided not to because clerics and druids are better then everybody at everything and it's really kinda annoying to have somebody tell you to "Just play a Cleric(or Druid)" when you ask for a good class for X thing.