Most decks will have some sort of site access, though few use the multi sites. I would not add all the sites I could of one color for the sole purpose of locking them down to one color, for a couple of reasons:
1. This hurts your deck, a lot. You have fewer cards for both offense and defense (remember, every 2 sites you put in means 1 less good card and 1 less evil card to use).
2. It just does not mesh. Sites need to give you some kind of other bonus. The only theme that doesn't care as much what their sites do is Heretics, since they protect souls that are in sites, but even they need ones with good abilities to justify the slot.
3. Any deck with site access will roll by you generally, because you have less staying power on defense due to the ratio of cards in your deck and that is your 'one shot' weapon that they ignore.
4. In T2, there tend to get to be a lot of souls out at once, and you aren't always going to be able to lock them up in sites. Lots of decks also have ways to gen souls, from your deck or otherwise, and that will hurt your cause.
