Blagh. All I'm going to say is that S2 should be designing Heroes that exercise the new engine and new concepts, like make bridges, deform terrain, spell-stealing, function-based shockwaves. Heroes specifically for ganking, for sieging, pushing, roaming, carrying.
The S2 Heroes you have mentioned are overpowered considering the former metagame. However, if the goal was to change metagame to focusing on pushing, then the former DotA Heroes would be considered weak in design and concept.
Even if the goal is to change the metagame from pushing to ganking, Heroes like PM and Maliken and Engineer cannot be said to be weak in concept and design. Exactly opposite, those Heroes are too powerful and synergize with themselves to well in combination with their current statistics. They require balancing, not redesigns. PM could be made slower, have lower damage to be a ganker, or lose some early game power with scaling in his abilities to become a powerhouse lategame. A Hero like Engineer could be made to be fragile, have lower base damage considering the stupid animation. His ability, Tinker, might be rebalanced to affect fewer stats of the tower, or have its siege-machine effects removed, or both. DotA rarely sees Heroes that are actually interesting like Morphling, Pitlord, nobody else except maybe Huskar, MAYBE. In RoC DotA, we saw Heroes like the Siege Tank and Mannaroth, who were absolutely DEVOTED to siege. Heroes like them, with such sharply defined roles that are "odd" in HoN, and yet have spells that are not seen like Siege mode. A Hero like Techies, perhaps, who stopped pushes and murdered creep-farming carries like there was no tomorrow, and was unique in how the Hero utilized traps and sh*t.
Consider a Hero, Holy Zealot for the sake of the argument.
-A nuke/heal like Accursed's, that is spammy but less powerful.
-A temporary physical armour buff of very high, average cooldown.
-A buff that temporarily increases an ally's Strength stat.
-A channeled ultimate that renders all other allies around the Holy Zealot invulnerable, perhaps as long as Jer's ultimate, perhaps a bit shorter.
And the Holy Zealot would take a role like Accursed, being STR support.
To me, he's UNBELIEVABLY broken, considering the massive massive amounts of EHP he can give his allies. He could ensure victory in both ganks and pushes. Or at least survival.
His merits are in the two spells we've yet to see: one that boosts an attribute for a short time and one that provides invulnerability.
With balancing, he could even with Jer, Acc, Nymph.
-Shorten PM's abilities.
-Decrease the stun or change it to a short slow. The push alone is strong.
-Lengthen FA's animation.
-Swift and Jugg are both broken to me. I mean, Jugg's wards move. They move! What the HELL.
-Chipper is stupid and needs have a more refined role, but his abilities are cool. Besides that, they only work well in a master's hands.
-Slither is stronger than before, but still seems balanced to me, if not a little in need of balancing.
-Hellbringer is just an all-around strong Hero, but his Death Boil is relatively broken.
-Chronos is brokenbrokenbrokenbroken. He was never balanced to begin with, having a f*cking permastun and ridiculous ultimate.
I say that ShredderIV had a good point: S2 is good at changing the metagame from gank to push. I dunno, I feel split. Should metagame become as it was from DotA, should it continue this way with buffs to all of the other Heroes? No, but then, it wouldn't feel like HoN, in going too far either way.
Sigh. All I want is to see abilities like the Fear debuff from Maliken, more pseudo-holds like PM's. If the metagame must be changed in order to suit cooler abilities, eh, so be it. Frankly, I want to see more tactical combat than super-intense picks. But... That's me.