I tend to play tanks alot.  I have been on several AE teams lately that have 2-3 tanks.  I had no problem letting one of them be lead tank or work together and agro larger mobs.  I try to go as fast as the team wants to.  Only a few times have I noticed a friendly rivalry brewing.  
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Tanks:
Hammer-Hand lvl 50 Inv/SS
Geo-Lithic lvl 50 Stone/Stone
Frozen Steele lvl 50 Ice/Ice
Agent Star lvl 42 Inv/EM
Syroth lvl 35 SD/DM