You're basically trying to optimize your character here. You know what you want, and are asking how to achieve it best - right?
To do that well, we need to know more about your character, most specifically, your stats. If you have a high charisma, then more levels of dragon shaman can be interesting. Secondly, it's useful to know what level ranges you will play - you're second level now, and you'll probably never reach 20th.
You're definitely going to want weapon focus, weapon specialization, and melee weapon mastery if you're a tank - but those are just three feats, and so you're not very dependent on more than 4 fighter levels.
You really lose as a tank by taking the 1st and 5th levels of dragon shaman and any other 3/4 BAB class. So, if you're going to take 1 level of dragon shaman, taking up to 3 more won't cost much, and if you take 5, then taking the next three won't cost you much. Specifically, if you have a high charisma, the dragon shaman can heal pretty reasonably at 6th level using his touch of vitality ability, and at 7th level you gain +1 natural armor (stacks with enhancement bonuses to natural armor such as amulets), which pretty much compensates for the lost BAB.
If you have a high charisma, you might also be interested in the marshal class (also online at
http://www.wizards.com/default.asp?x=dnd/ex/20030906b ). This class has a minor aura with a bonus equal to your charisma modifier. There's an dexterity-checks aura which for instance applies to initiative checks, and has a pretty handy 4th level ability (grant move action).
So the real question is, what is your charisma, and what level range will you play?