If they fixed that then ignore me. I haven't actually used a Radiance as a tank in forever because I never heard about that being fixed and quite frankly there are better early game synergies so by the time I'd grab one for the sake of it I'd just pump armour and detonate.
Aye. part of the problem is that it can't really function as a tank even with the taunt functioning. It's really no more durable then any other capitalship(if you're relying on the extra armor your shields are already down radiance is in danger and making the enemy focus radiance is the last thing you want to do). More to the point, no capital ships can bear the focus of late game fleets, especially advent capital ships which are squishier then their TEC/vasari counterparts.
For Animosity to really be beneficial, damage dealt to the Radiance during it's effect has to be in part "wasted". The opponent needs to really regret that that damage isn't going somewhere else.
The simplest way to accomplish that is to add a secondary effect to animosity that mitigates incoming damage to the radiance. If Animosity also gave +4/6/8/10% max shield mitigation while active(roughly a 30-40% damage reduction at rank 4 dependent on how much other shield mitigation bonus has been researched), animosity would really constitute a net loss for the opponent(-30-40% damage to upwards of 30 ships in their fleet, but all of the damage those ships dod eal is focused on radiance).
With a mitigation bonus during animosity Radiance may actually be tanky enough that forcing enemies to attack it is actually significantly beneficial.
note a shield mitigation boost is not the only way this could be accomplished: a straight % damage reduction(such as in the Kol's adaptive forceshield) or some sort of debuff to affected ships(-accuracy or weapon speed) would also do the job nicely. I favor shield mitigation chiefly because it fits the advent's image and they already have a bunch of attack speed-accuracy options on their ships.
Regardless I doubt such changes would be overboard as animosity is only up 20 out of 35 seconds(just a bit more then half the time).