I don't have too much issues keeping concentration spells active and in my opinion they are quite powerful. At lower levels I mostly just used bless, but now in act 3 spells like dominate person or wall of fire have decided more than one fight in my favour.
To keep my concentration spells running I use a combination of high AC on my casters (20+), breaking line of sight, multiple options to prevent enemy movement and counterspell against the worst enemy spells.
