I have recently had my tyres on my bike changed from mountain bike tyres to road tyres. I was also advised by the man who fixed it that my saddle was too low for me and he raised it. Since these changes it almost feels like I am cycling with slightly flat tyres. Uphill doesn't feel massively strenuous but I just wanted to see if this is normal or not?
Re: your saddle being too low.
One way to check if it's at the correct height is to sit on your seat, put one foot on the pedal and try to "straighten" your leg - with the pedal at it's lowest point (the other being at the top) there should be a slight bend to your leg.
This video's quite informative: seat height
Raising the seat height will allow for a more efficient pedal stroke. Too low a seat height tends to "burn" the thigh muscles. And cause a loss of power - especially on the down-stroke as you come through the pedals.
The main difference by changing from mountain bike to road tires will be the tire pressure. Road tires - even on MTB - are pumped up to a higher psi than off-road tyre. Consequently the contact patch is smaller with the road and the rolling resistance reduced. A side-effect of this would be the sound and feel of your tires on tarmac will be different to your old tires.
There is no correlation between tyres and seat height that I know of. Road tyres are not as high, so with them on the bike itself would be a bit lower overall. But that's got nothing to do with the seat.
So my 29'er mountain bike and my 700 touring bike both have the same seat height in relation to the pedals, but the touring bike sits lower to the ground and took a tiny bit of getting used to. Both in looking at the pathetically little bit of rubber between me and the road and handling-wise. I still feel happier with the bigger fatter tyres, especially when throwing the bike around.
So I wouldn't think this is normal, unless the guy had another reason for raising the seat.