Oh you mean the puller flag in the group role, not the PullerTank role in KA? I don't think that does anything in KA, I think KA only looks for the Main Assist role for any functionality (e.g. if you set heals/buffs only to land on the MA).
The PullerTank KA role makes that character automatically go out and pull mobs and tank them. It has nothing to do with buffs.
Buffing tends to happen out of combat -KA will check what's happening right now and will do stuff in pretty strict order. Like, sometimes my buffers will be buffing and my puller gets a mob in camp. Shit happens; it's automation software. I tend to put short term buffs in the DPS section as that gets triggered with a mob in camp.
KA doesn't rely on Dannet for buffing- many people simply can't use Dannet. For different geo locations I thought most people used EQBC instead anyway, no need to set up a peer to peer network. And tbh, two sets of boxers don't even need to have that connection UNLESS you want to issue commands to their PC using EQBCS/Dannet, in which case why bother having the other person there (unless you're just using their hardware and they are AFK I guess).
If you're experiencing lag it might be worth just ditching the P2P network and/or Dannet, it *might* be that Dannet is taking a long time over the network and causing pauses etc?