I also did this analysis on healing on magic vs 5* troops
Tanks who do not heal, will be able to take much more punishment.
Example: Brimstone
(I calculated robustness as Def + HP/2)
Is the 25% increase in Robustness worth it for the lower mana gain? It will certainly catch some opponents of guard.
But how will this affect tanks who heal?
Myoin-Ni comes to mind
Bear in mind she needs a different class troop.
Myoin boosts health a set amount, so her healing will not be affected by her increased HP, and she will have lost the 22% healing bonus.
But on first/second/third charge this means 81/117/132 HP. While her base HP has increased with 832 HP and her def has increased. That is a more than fair trade.
If the hero heals in %, that makes the case even better. If a support hero is to heal Myoin-Ni in these different set-ups with a standard 40% regular heal, the potential is the following:
(I have included the healing bonus from troops only, as other factors like emblems will stay the same)
She will still heal 15% more then with the healing bonus from troops, due to the high HP
Also – the passives play a part, but some of these are hard to utilize. For the two above, Brimstone is a barbarian and gets +8% effectiveness from attack buffs. So he is dependent on the buff, but he has attack up as a aether power. Myoin-Ni is a druid and gets -10% damage from ailments. This is timeless, so more useful in some cases, but a burn from Aradia will still hurt at 90%
To me it seems that Rogue, Cleric and Sorcerer are most universally useful, alongside Wizard if they deal damage with their special
So I conclude that tanks, both non-healing and healing will benefit from the legendary troops.
Sorry for the dark text in the tables