In discipline gear renew ticks for 14397 and crits are 14974, which is indeed 4%. It is probably a bug that will be corrected.
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Let us put it all together now.
For holy assuming 19% buffed crit and 32% buffed mastery, 15% haste and 12k spirit, the amplification buff is worth 2.66% crit, 1.54% mastery, 1.05% haste and 840 spirit. This is equivalent to a grand total of 3 872.25. To convert that to a % increase in healing
% increase = (1+crit*1.14)*(0.993+1.07*mastery)*(1+haste*1.07)/[(1+crit)*(1+mastery)*(1+haste)] = (1+0.19*1.14)*(0.993+1.07*0.32)*(1+1.07*0.15)/(1.19*1.32*1.15) = 1.043723821824
a 4.37% increase in healing is equivalent to ~1960 intellect.
Hence the 7% amplification buff is equivalent to 1960 intellect and 840 spirit.
the intellect proc is equivalent to 1960 intellect as well so the grand total is 3920 intellect and 840 spirit. If we compare it with the full buffed hc horridons trinket, which equivalent to 1785 intellect and 1.7k spirit we see that the amplification trinket is more than twice as much throughput, but about half as much regen.
However this does not take overhealing into account, since intellect is much less susceptible to overhealing than crit. The cleave trinket has the same intellect proc but it has 3.11% chance to duplicate a heal and divide it between up to 5 nearby targets. On paper that is 3.11% more healing assuming it procs off every heal. Hence the cleave trinket is worth a 3.11% increase in healing and 1960 intellect compared with a 4.37% increase in healing, 1960 intellect and 840 spirit. However that is before overheal. In real terms I think the multistrike trinket might actually come on top for holy.
The multistrike trinket has 14% chance to do 33% additional healing so a 4.29% increase in healing before overheal. The intellect proc is also 1960 if it procs exactly once per minute. For holy the multistrike trinket has the highest overheal potential, so it is probably behind the amp and cleave trinkets.
For disc with 35% crit, 35% mastery, 10k spirit and 9% buffed haste, the amplification buff is worth
For disc the amplification buff is worth overall ~5.46% healing before overheal. This is due to a 2.47% increase in healing and a 9.5% increase in aegis (from increased crit amount + the buff to mastery). PWS is buffed by 4.84%. With 10k spirit you also get 700 more spirit. So for disc given the important of aegis and spirit shell the amplification trinket is by far the biggest boost.
Conclusion: the amp trinket is the best throughput trinket for disc easily worth in excess of 2% total healing more than the other trinkets. The amp trinket is probably not as good as the cleave trinket for holy.
On paper all trinkets have proc int worth on average ~1960. Ignoring overheal the multistrike trinket is 4.29% more healing, the cleave trinket is 3.11% more raw healing and the amp trinket is 4.37% more healing for holy and 5.46% more healing for disc.
The trinket represents a 9.5% increase in aegis. At 35% crit you will need 0.35*1.095 = 0.38325, or 3.325% extra crit to produce a 9.5% increase in aegis.