Both the Neruda and the Voruntak are good. Herald, not so much.
Neruda gives the owner an income boost, the ally a trade boost, and raises population growth rate dramatically.
Herald increases culture production, increases current allegiance, and blows up.
Voruntak increases production and extraction rates, current planet health, and makes planet invulnerable for a short period. Seems to me that Mutual Threat is an undervalued ability. It's very powerful. It's just not boosting yourself. 
