Is it better to add a point to Vengeance or to Conviction? This is the question I hope to address. First we need to discuss what we mean by better. Are we asking if one way adds more damage or if it is more mana-efficient? Let us try to answer both questions.
To begin with, here is some information about Vengeance:
1 2 3 4 5 6
4 4.2 4.5 4.7 5 5.2
70 76 82 88 94 100
The first row is the skill level. The second row is the mana cost (note that it goes up in alternating increments of .2 and .3). The last row is the percentage of Elemental damage added for each element (Fire, Cold, Lightning) which goes up in increments of 6.
Here is some information about Conviction:
1 2 3 4 5 6
30 35 40 45 50 55
The first row is the skill level. The second row is the amount that the enemys resistance is reduced by.
For the sake of convenience we are going to use a weapon which does 100 pts of Physical damage and there will be no other sources of damage included. We are also assuming that the monster has base 0% resistance across the board.
The following (1:1) will be used below with the first value referring to the skill level of Vengeance and the second value referring to the skill level of Conviction.
1:1 100 210 * 1.3 273
2:1 100 228 * 1.3 296
1:2 100 210 * 1.35 284
5:1 100 282 * 1.3 367
1:5 100 210 * 1.5 315
The first column represents the respective skill levels. The second column is just to remind the reader that we are using a 100 pt damage weapon. The third column shows the Vengeance damage (which is 3 times the listed damage for that level) times the damage increase caused by Conviction. The last column shows the total Elemental damage caused.
From this table it should be clear that, in general, it would be better to place additional points into Vengeance rather than Conviction if the intent is to maximize the damage.
Now we need to look at damage per mana
1:1 273/4 68.25
2:1 296/4.2 70.48
1:2 284/4 71.00
5:1 367/5 73.40
1:5 315/4 78.75
The first column is the same as in the previous table. The second column is total Elemental damage divided by the mana cost of Vengeance at the specified level. The final column is the result of the second column.
As we can see, it is more mana efficient to place points into Conviction than into Vengeance.
We leave it to the reader to decide which form of better that he/she prefers.