There are many ways to fix the sniper problem:
- Make strike teams unique
- Make strike teams a detachment
- Limit the snipers range (2-4, 3+, 1-4, lots of options)
- Increase cost
- Remove keywords
- Make the sniper exhaust
It doesn't matter which combination of the above they go with.
I don't think terrain is a good solution. In any given tournament there should be tables with a variety of terrain. On any given table there should be different areas with different types of terrain. That variety keeps things interesting and makes different units shine in different circumstances.