I took a less than inspired path in WoT and have more or less been focusing on Russian Heavies. From my perspective, the KV-3 is a monster, and really needed the tier bump to VII. The fact some people miss is that like american, french, and german heavies, there's a particular way to play them that makes them more effective.
The KV-3 in WoT is not made for head on engagements in high tier matches. The 175mm of pen the 122mm gives you makes that fairly obvious. So what's a heavy to do if it can't face-hug other heavies? For starters, 175mm of penetration is more than adequate enough to blast a hole straight through the side armor, rear armor, or turret side of most of the tier 8-9 tanks. Studying your target for a moment to ensure you're not shooting at sloped or angled armor is a skill you should already have, and the aim time of the D25T will give you plenty of time to think. Let the battle lines be drawn by the higher tier bruisers, and find a squishy spot on something. Putting yourself in a situation where you will meet heavies head on or a wolfpack of mediums happens, but the chances of that happening will be low if you have some experience.
Another scenario the KV-3 excels at is peekaboo. With a building as your armor, the exposed armor angled, and the D25T's high alpha, no wonder it works so well. It's easy to compensate for reload time when you just have to back up. The mass of the KV-3 and torque of the tier IX engine makes the vehicle rock when accelerating, which can be used to great effect when you have to engage head on. I won a one-on-one with an AMX 50 100 by bouncing shells that way. I've also held back a pack of 3 Tiger Ps in Ensk. (True stories, and the Tiger P is only good on paper in my experience fighting it.)
The KV-3 also has a nice large gun mantlet, which discourages people from hitting your turret and makes them shoot at your rather absorbent tracks.
The bad part of this tank in my experience is when you're stuck out in the open. You're a sitting duck and it's likely you'll be tracked and killed by something with decent accuracy or arty. Versus mediums or lower tier tanks, the KV-3 becomes a playground bully, and it's up to the arty to end your reign of terror.
My rule of thumb is to always be close to cover. Cover and patience will make up for a lot of what the KV-3 might lack and make the enemy engage you on your terms.
TL;DR: The KV-3 is a monster in the right hands. YMMV, but it is certainly not "bad".