I've got foot crossbower char for once. Standart build 15\24, 160 in xbow 85 in 2H. Nonheirloomed Sniper and Steel bolts. IMHO this build was too good to be balanced. Yes, I was an archer for 20 gens, so I know how to shoot people. But with 3,5-1 overall k\d with this char, all I can say - xbow bonuses from heirloom is too good to be true.
I have this build also, and it is incredibly situational. k/d's are a poor indicator for class balance. I have had a high k/d for every class I have played simply because I work out how to get the most out of them. The 85/160 crossbowman with an Arbalest's performance depends greatly on the map and game mode in question (defending on siege being the best). For maximum efficiency you must aim at targets unaware of you, for you are unlikely to hit a target that is aware and will dodge. You must essentially be a sniper, shoot, skirmish, hide. And what are snipers good for except good k/ds? %80 of my Crossbow kills are unaware of my presence or location.
For example one melee with a shield is aware of you and enclosing at 10m. To his right, there is another melee running the other direction at a ninety degree angle. Commonly I will shoot the ninety degree enemy, most likely not killing him unless he has been hit before or is wearing a shirt, then focus on the one targeting me. Then, I will either fall back to friendlies if available, or attempt to kill him in melee.
This situation most commonly arises in battle, which is generally harder for this class, particularly on plains. Your long reload makes you succeptible to cavalry, other ranged, and most annoyingly cavalry archers. With the latter, if you miss or do not kill with your first shot, unless you have support you are stuffed. Most commonly in battle I find my Millitary Pick
picking up more kills than my crossbow because I can't get off enough shots before the battle is joined and people generally underestimate a crossbowman's ability in melee.
Frankly, I do not think crossbows are overpowered. They were fine in the previous patch before this two slot nonsense, take away two slots and remove the damage bonus. It's archery that is feeble.