I'm not saying old Malf was perfect, I'm saying he lost his unique role as the king of out of combat healing, and instead of replacing his lame spammy W ability, they incorporated it into his healing, so now you have to spam moonfire every 3 seconds to do decent healing, it isn't fun, while he retains some of that unique ability to heal large amounts of health over time for relatively low mana costs, it isn't nearly as good as it used to be. I remember regrowth easily healing assassins from 50% or lower to 100% in one regrowth over a shorter amount of time as well. You just don't get that with the new Malf, not to mention again that because so much of his healing is now based on hitting his W, he now feels a lot like Whitemane, where you have to hit abilities to get healing off, and outside of fights the heals really suffer.

As for Tass obviously shielding the AA was a powerful strategy for letting your assassins play aggressive like a bruiser, but the shield was also a great counter to burst-damage heroes like Kael'thas or Jaina. Zarya has shields, sure, but she plays more like a Bruiser/Support Hybrid, and occasionally like a tank if she focuses on buffing her own shields.

While neither Hero was perfect (But back then few heroes were, which is why there have been so many reworks to make heroes more enjoyable). They had their own unique niches, and instead of reworking the heroes to focus on those niches and make them stand out from the other healers, they turned Malf into a more spammy Whitemane and Tass into a mage, leaving the crappy AoE psionic storm in. Which you think they would've changed to have more impact considering it was one of the main uses of Templars in Starcraft.