**Thunderlord's Decree**, currently Tier 3 choice in the utility-focused tree hardly makes any sense there, considering that support minded players aren't going to be building a lot of AP or bonus AD, and will get no value from minor aoe damage. Thus, having a talent focused on offensive stats will likely be wasted. However, it can find good use in the tanking tree, swapping places with **Grasp of the Undying**.
Grasp of the Undying provides a useful heal mechanic on the next hit with a small cool down, something that would tremendously useful for many support tanks to pick, while still providing a strong decision point between stronger heals/shields or personal sustain. Additionally, Thunderlord's Decree would fit nicely at the top of the tanking tree **IF** it would lose the total AD and AP scaling in favor of a much more tank-focused stat of either bonus health, max health, bonus AR/MR, etc. It would provide an actual talent choice to the tank with providing a little more damage in the form of a 30 sec CD aoe versus a damage reduction talent.
Further, it would provide a talent choice to the jungler as well, given that he may pick to have some aoe for jungle clears (certainly, total health would be the best scaling stat to provide some value during the early game).