I have bought quite a few site unseen and my experience was that its NOT that hard.
First I like to research the market and learn as much as I can and get familiar with "my patch" im interested in. btw, I use RP data Professional and I find it INDESPENSIBLE.
Then once I have a good understanding of what im dealing with I like to (if possible) fly down and have a look at the general area for a few days (might buy at that time or buy following months)
For particular properties im interested in, I have used agents to take details photos for me and make it clear to them that im buying site largely unseen and if they take only 3 or 4 crappy photos its not likely im gonna be interested. Most agents do a decent job at taking photos, some cant be bothered and that's fine.
then its all down to B&P. Really by that stage you should have a good idea if you like the place or not.
RP data gives me all kinds of valuable info on the place, eg
1. what the current owner paid
2. Ownership..eg husband and wife, or single, or whatever...that actually lets you get into the mindset of the seller (very valuable advantage)
3. Lets you look at recent 12 months, 2 years etc sales
4. Lets you see the boundaries of the place, even how many meters frontage is etc (more so important for development)
5. Shows you how many days its on the market and how they have come down in asking price over time (again great negotiating advantage to have this)
6. Even often gives you the direct contact numbers of the vendors!!
you can learn all the above 1-6 in a matter of minutes and start to put together a picture and learn a lot.
ok ill shut up now too long a post