Doesn't seem bad to me...
This doesn't seem cheesy to me. You're using a 3rd level and 2nd level spell to support your melee combatant and it is proving very effective against ogres and the like. I would think that if you cast Displacement and Bull's Strength on your tank fighter he'd be very effective too.
This will probably stop being so effective eventually because:
1) You'll end up fighting a group who's familiar with your tactics. They can use various spells or abilities to counter this tactic (Dispel Magic, their own Blindsight, etc). This isn't cheesy, any intelligent group that sees you fight once (or hears that you use this tactic) will be prepared.
2)You'll go up in level and find more and more of your opponents have enhanced senses, blindfighting feat, enhanced mobility (flying would stop this tactic for example). More powerful opponents will be less susceptible to this without the DM only throwing bats and undead at you.
So, in the mean time, you have a tactic that is very effective against a fair number of foes. Enjoy it, it's not going to last forever but the DM shouldn't take special action just because you're doing well. That's what having cool abilities is about.