Fighters seems to have a much higher # of potential target engaged. If i choose to make a multiclass tank with no fighter class, how good can i expect to tank? Im thinking about a paladin/chanter or a paladin/stalker.

Paladin with Shieldbearer gets +1 while wielding a shield, you use a spear you get another +1 and there's a skill you can take that gives you another +1 so that's four not including any additional engagements you'll get from items you're wearing.