need help with lighting groups

wedding groups shots in church after the ceremony i always have light
fall on the corners .

24-70 2.8l exposure 125/4.5 i hate bumbing up the iso but do but still
am not happy doing that .
im using a canond 5d with the quantum t5d-r on a custom bracket .
i shooot raw and have a little room to open them up more but was
thinking about adding another light to get even lighting .
do any of you guys/girls have any experience with this type of
lighting ?
do any of you bring along studio strobes and use them for these shots ?

Several ideas:
(1) retouch and brighten the corners
(2) bring large strobes and light stands if you have the time to set up the
equipment.
(3) arrange large group in a arc instead of a line, this way the center
people receive the same light as the edge people
(4) no time to prepare? take two identical photos, one with more exposures
so you can combine them into evenly lit photo