Hey. SO my two cents on the hero/explorer.
I think the explorer is good, no doubt about it, but has significant weaknesses. slower than IN, batleship maneuverability. 4+ in he rear, no real weapons aside from bays (str what, 6 batteries? Not a real gun) 1 shield...These make it balanced, as any cruiser firing at it will almost always inflict damage, and it can't really brace, as it can't escape the fight, and is a free 230 VP without bays.
The Hero does not match it's fluff, that's fair. However stats wise, I think (regardless of what you think it's weapon load-out should be) it should be aggressively costed, as without it, old school Tau are too disadvantaged to really win. without a decent-good warship, the fragility of the battleships and terribleness of the merchant is just too much. IN cruise forward on AAF, shotgun, next turn broadsides, DONE. with the hero, there is something that they have to engage, and respect in combat, whereas as I mentioned with the other ships they're not even really worth bracing against all that much (obviously specific situations arise, but you get the drift). it's just too lopsided as a fleet.