Dude, play your game how you like. But, I don't think the vampire needs any tooling. Look at the templates. +2 goes with Liches, Lycanthropes, Half Fiends, half Dragons, Ghosts, etc.
Now, look at other 7 CR critters. Water Naga, Umber Hulk, Medusa, Hill Giant, Flesh Golem, Drider, Dire Bear Chuul, Bulette, Black Pudding, Barbazu, Aboleth, Blue Juvinile Dragon, Yuan-Ti, Abomination.
Now, a lot of these things are really different, compared to others. Some are easier to kill then others.
The Remorhaz doesn't need tooling. Yes, it will eat you alive, but it has severe weaknesses which make it weak. First of all, it has No Ranged Attacks. A 7th level mage's first step should be getting the party Out of there: A fly, if not several, and a levitate. Then, start peppering the thing with ranged weapons and spells. It stands no chance. But if you charge it, you're going to die. Next, it's will save is a +3. That's just *aching* for spell smacking.
Compare all CR 7 creatures to a 7th level character. No, they just don't compare. Maybe that's why 4 7th level PC's shouldn't be fighting a single 7th level NPC. However, 4 3rd level PCs, or 5th level PCs will be challanged.
My party of 4 6th level PCs faced a 7th level dwarven fighter vampire (CR 9). They didn't kill him, but they reduced him to 0 once, killed his spawn, his 6th level Fighter/rogue vampire cohort (a former character), and the only reason he *did* survive was because he ran, to plague them again.
