Hey Blarg, meant to get back to this but I'm just going to start typing it out instead of quoting all that.
Basically, I feel like the Harrower has some deficiencies and it may have some use with 'casters that can overcome them, but otherwise it is probably not so great.
Pros:
Thresher
Guns are always handy
2" melee
Pathfinder
Steady
Neither here nor there:
Potential to power up as the game goes on (but can compete with some 'casters and models)
Middling threat range in the Cryx helljack stable
With the "Pros" I think you hit on the obvious ones, but you missed a couple of things. If it were any other warjack with simply one good melee weapon and one ranged weapon, then the "Guns are always handy" line would be applicable. But you have passed over 2 related special rules that bear mention: Quick Work and Wraith Shot. Off the top of my head, I don't know of any other warjack that has Quick Work - it's pretty damn rare among warcasters, nevermind warjacks. And I don't know of any other unit that has Wraith Shot. Ghost Shot you can Find, Wraith Shot seems kinda special.
One of the other things that caught my attention about the Harrower is that instead of being a bunch of special rules where you might use one here and one there, it is a package that has great potential to work all at the same time. Let's say that you charge your Harrower into a group of infantry and Thresher(1) them. You end up killing 3 of them, so Quick Work(2) allows you to make a ranged attack. You take one of the souls collected via Soul Taker - Spirit Harvester(3) and make your ranged attack a Wraith Shot(4) that can ignore LOS, concealment, cover and gets its attack and damage rolls boosted. That's 4! special rules all used in a single activation. But we're not done - if the ranged attack goes somewhere far away the Harrower is still going to have 2 souls to convert to focus next turn, making it fully loaded. If that AOE3 goes into the nearby infantry any of them killed within 5" will have their souls collected by the Harrower, further fueling it for later.
One last thing about all of these Pros: After reading my comments about some of the Cons, keep in mind that this non-character warjack only costs 16 points.
"Still fragile for a linebreaker role, likely will not survive retaliation"
The Harrower has the same DEF, ARM, and damage grid as the Ironclad. I don't think it's fragile. It's not a Juggernaut, but then you're getting into Khador's bailywick, which is my other other point - We're talking Cryx here. Generally speaking, Cryx isn't supposed to take a beating, it is supposed to deliver a beating and hope that no significant beating is coming back.
"Low POW on melee and ranged"
The melee weapon is POW 16, just like the Death Claws on the Slayer and the Helldriver on the Reaper. Not bad for Cryx, if you want higher POW on your warjacks you're either looking at losing reach (and Thresher, and Spirit Harvester, and...) or getting into character warjack territory.
The POW 12 on the ranged weapon is kinda low. But it is an AOE 3. With the Wraith Shot ability to get boosted attack and damage rolls that ignore LOS, concealment and cover. On a warjack with Quick Work. That is not a character warjack and only costs 16 points.
"Low attack volume vs. single target"
Yup. This is the same problem almost every other warjack that has 1 ranged and 1 melee weapon has. The other 2 crabjacks have the same problem, as well as the Corruptor.
"Middling MAT and RAT"
I won't argue with that, especially when you first start getting into the thick of combat. But but to hammer on a point, it reminds me of a time when there was a newer player complaining about the Berserker back in Mk2. He complained about how terrible it was with the low MAT, DEF, and ARM, but once I pointed out the 2x axe attacks and the cost, he immediately smiled and said "Oh, well let me go get a couple of them." Yes, the Harrower only has MAT 6 and RAT 5 - but with everything else it has, what more do you want for 16 points?
I won't argue regarding any of this, because I can't, I'm not a hard-core Cryx player, I'm a Khador player that dabbles in theme armies in other factions. But it seems like you're talking more about problems with Cryx than problems with the Harrower. Compared to more "military" factions like Cygnar and Khador, Cryx has some huge problems and huge advantages. The Harrower's design seems to fit in just fine with the rest of the Cryx.
If you read some of the other people who have posted in this thread they either come out as completely either in favor or not for the Harrower. I'm not going to say that one side is right or one side is wrong, because I think it really depends on the player, how they play, what warcasters they use, and what they go up against on a regular basis. If there is one thing that I think we can all agree on, is that the Harrower suffers from a lack of infantry targets in general. I blame that on the changes to done in Mk3 and how everyone reacted to them. Give it time and as everyone starts backing off of the jack spam and SR2017 starts pulling in more infantry you'll see the Harrower become a more interesting investment.
And again, I'm not trying to get anyone to join the Harrower Fan Club. It just seems like you Cryx guys don't appreciate what seems to me to be an unusually well designed package. That's all.