I hate having to obscure items by having more than one deep on a display shelf, but as a collection grows and space becomes a premium, you have to make sacrifices.

As you've noted, have the taller figures at the back to see as much of them as you can.
If the set or series are all about the same size, and you don't want to have figures standing on blocks to vary the heights (to show off their similar, unaltered size scale), have them on a shelf with a lot of space above it (adjust the next shelf above). That way, if they are all about the same size (like a collection of Generations/Classic-verse that are mostly Deluxe class), you can look down over them more without the shelf above getting in the way.

Also, alternate colours, to prevent one colour from being grouped together too much, effectively "hiding" a toy in the middle or back (like a "where's Wally" picture).
Unless of course you are going for a "character themed" displays... which aims to look impressive from a distance.