The issue with Deathfire Touch

http://i.imgur.com/JMBQmuk.png

As someone who loves DoT damage, I became instantly attracted to this mastery. Additional DoT magic damage on any mage I play! At first, I wanted to use this for certain AD champions as well, but quickly realized it's not the best idea. :|

Anyway, I want to be able to take this mastery on any mage I play and not feel bad about it, as if I should have Thunderlord's Decree instead because reasons. I was thinking about why it feels bad to go for DFT and not the FotM, especially on a DoT mage like Malzahar (my main mage) who additionally has physical damage from voidlings, when I realized what the real issue is.

Both of the 3rd tier 5-point masteries in Ferocity are much weaker than the flat armor/MR pen mastery in the Cunning tree. This alone is a valid reason for many to go for Thunderlord's Decree over DFT.

Yes, % pen is better against enemies who invest in a lot of armor/MR, but 7% is very little (7 armor or MR ignored for every 100!). Needless to say, it's garbage against squishies, unlike flat pen. Who are the ones to focus in fights: tanks or the squishy damage dealers?

The amount you gain from the flat pen mastery, plus the fact you get both forms of pen, makes it have more of an impact on anyone you play and play against since the magic pen compliments the TD proc. The % pen can be easily acquired from Void Staff or one of the Last Whisper items, which are typical to buy for any high-damage dealer anyway, unlike most flat pen items. What's worse is If you have the 7% magic pen mastery, you lose about 3% from it after it's stacked multiplicatively with Void Staff (35% --> 39.5%). That's not a major increase in damage. Flat magic pen is almost always much more attractive to go with Void Staff because of this.

The % pen masteries need to be buffed to compete with the flat pen mastery. Simple as that.

The best solution in my opinion is to combine the two into one (like with the flat pen mastery and what we had last season), both values increased to 10%, and introduce a new mastery in the same tier that does something different for those who want one of the Ferocity keystone masteries but don't want % pen.

An alternative (or addition?) is to give DFT level scaling damage so it can directly compete with TD. I don't see why TD can have it but not DFT. The scaling amount doesn't need to be the same as TD. Start at 5 base damage and increase by 5 per level (90 at level 18). Heck, I would even accept 3 damage per level (if starting at 5, 56 at level 18). That should be reasonable. Keep in mind TD has 180 base damage at level 18, making it incredibly effective even on tanky fighters. I don't see DFT with higher base damage making it stupid strong, even with its current AP/AD scalings. By that point in the match, the damage would still be diminished considerably with merely one major MR item, like it is now. The level scaling would only help nudge it to become more of a valid alternative to TD for mages who can't use TD as effectively as others.