People will vote a Healer for mvp,if they realize you've healed them.Some warzones,there so much chaos,and you're pumping out heals and noone notices---because they are focused to their combat and they might not see your name over their heads in green -healing spam.Hey,it happens.
If they do see your name in green healing spam,and you saved their carcass,they will vote you MVP.Newbie players tend not to vote healers MVP,because they really don't understand WZ's yet---some of them think WZ's are team-death match.But veteran players will vote for you.
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This, exactly. While on average, I tend to get several MVP votes per match for healing, it all depends on the team & the situation.