The fiend folio gives us two devas: the stronger monadic ones, tasked with guarding the elemental planes, and the weaker movanic, who can be found on the material and energy planes.
10 RHD, with all the traits you'd expect of a mid-level celestial. 90 ft. fly speed is impressive, DR 10/evil sure to come in handy, and all-around good stats (+6 to +10 bonuses) are neat to have. SR 22 has its uses.
Immunity to acid, cold, electricty, fire, planar effects, suffocation, death effects, ability drain, ability damage, and energy drain makes for an impressive list of things that you get to no-sell, especially combined with the innate Magic Circle Against Evil and Minor Globe of Invulnerability all devas can project. Flanking should be less of an issue for you than for many other characters, but Uncanny Dodge still has its uses, too.
Most important, however, is the enormous list of SLAs. Naming them all would take too much time, but the highlights include at-will Create Food and Water, Hold Monster, and Polymorph, 3/day Dispel Magic and Plane Shift, and 1/day Commune and Raise Dead, with many less important spells to round this out.
The monadic deva offers a strong chassis, as well as a good array of magic, and I could easily see one outperforming an at-level cleric in many respects. However, the lack of true casting limits its advancement, as well as its flexibility. Even so, +2 is fair.
Only 6 RHD, but similar to monadics in many respects. DR 10/evil is still there, SR has been slightly downgraded to 19, and the ability to survive elemental planes now protects against those with positive or negative energy. The energy immunities are mostly still there, but the fire immunity is now merely resistance 20 (ironically, the devas with actual flaming swords are more vulnerable to fire). Ability scores are still uniformly boosted, just to a smaller extent.
Soothing Presence of Nature prevents all plants and animals from attacking the deva unless magically compelled (by RAW, this applies even while you are slowly beating them to death), which is good enough to autowin you some encounters. Heavenly Deflection is either a neat ability that allows you to no-sell one targeted ranged attack per turn (provided you make a moderately hard reflex save), or it's a ridiculously niche perk that forces you into using a very specific weapon.
The spell-likes are once more plentiful, and many of the monadic's stronger ones (at-will Polymorph, 3/day Plane Shift, 1/day Commune and Raise Dead) are available here as well. In light of that, I think +2 is the very minimum here, with a strong case for +3 to be made.