Am I missing something? Why would I want to upgrade to a new merc and have to restart the painfully long process of leveling them up?
The mercenary battalion buff is better with the newer mercenaries. You can get them pretty cheap on the broker or via mission rewards. When I actually need a merc up, I pop the Golden Inquisitor, because he heals, cures, and rezzes, and he's level 20. But the Mercenary Battalion Buff goes by "seasons", and you get much better stat boosts from the BoL mercs. I personally think the Battalion buff is best from Rosa Dod, YMMV. The trick is to not just get as many of the BoL mercs as possible, but also to level them to increase the size of the Battalion buff. I summon Rosa Dod then dismiss her to get the right Battalion Buff up. I'm leveling her, but since I don't ever use her for anything else, I'm not spending any time gearing her out.
As long as you have a merc that meets your needs and you're not focused on min/maxing everything, then there is no reason to change mercs or worry about the merc battalion buff. Zhugrus meets my needs so I use him and none others.
I've just hit 40 (actually 46) contribution to the merc battalion buff. I have Tarsil (20), Rosa (20), Zel'Kriaz (20) and Horthis (currently 13). When my contribution ticked past 40 to get the next stage of the buff, I gained 0.3 fervor. Erm.. thanks?
