As you have probably read, if you are following the changes in the combat system, in the expansion there are some significant changes to how combat damage is calculated.
Most of these changes "come out in the wash," as it were, but this post is an attempt to explain a few of the changes as they pertain to LM.
Tactical Damage Rank on Staves
One big change is that melee DPS is fixed on staves, and cannot be ranked up by adding legacy points. Instead, all staves get a Tactical Damage Rank (TDR) legacy which functions very similarly to the DPS rating on a melee or ranged weapon. This legacy can be ranked, and affects the damage of our tactical skills.
LM's below Level 50, without a legendary staff, have a TDR equal to their character level, I believe. I have not studied how low-level LM skill damage changes, so I won't discuss this case further.
An LM above Level 50 wielding a non-legendary staff has a TDR of 50. Otherwise, your TDR is determined by the rank of corresponding legacy on your staff. These legacies start at TDR 1 (for LIs around Level 50) and go up to TDR 18 (Level 65 3rd Age). I have not seen a Level 65 2nd Age, but the maximum TDR rank is probably 19 or 20 on those.
The TDR Rank on your LI should be added to 50. Thus, with a maxed L65 Third Age (TDR18), your TDR is 68. This is shown on your character panel, near melee weapon DPS.
The legacy point costs to rank up TDR are identical to the costs to rank up melee DPS on staves now. You can max the TDR once the item is at least Level 22.
TDR and Tactical Skill Base Damage
All of our tactical skills now do variable damage based on the TDR of our staff. Again, this is quite similar to melee and ranged skills, which usually have a tooltip which reads something like "Main-hand Weapon + X damage". (However note that in SoM, the tooltips have been simplified to list only the minimum and maximum damage, taking into account relevant bonuses).
TDR is equivalent to "Main-hand Weapon". Our skills appear to have a component which scales with the TDR, and a constant component. Adding one rank of TDR adds a fixed amount of damage to a given skill. In other words, going from Rank 10 to Rank 11 adds exactly as much damage as going from Rank 17 to Rank 18. All skills also have a fixed component which does not depend on the TDR. Thus, TDR rank does not correspond to a percentage increase in damage, rather each rank provides a fixed bonus to the base skill damage (although this bonus is different skill-to-skill). For example, each rank of TDR adds roughly 2.5 points to the base damage of Burning Embers, but adds about 8 points to the base damage of Ents.
Another change from Mines of Moria is that our Tactical Skills do not do fixed damage, but have a range between a minimum and maximum. This range appears to be a fairly constant +/-17.5% of the average for all skills.
To develop a model of how various bonuses stack, in what follows, I will call the damage determined from the TDR the "Base Skill Damage", B.
The Base Skill Damage is calculated as:
B = C*(TDR) + D
where C and D are different for every skill, and TDR is the Tactical Damage Rank determined by your level or your staff. C and D may be dependent on character level as well; I have only studied a Level 65 Lore-masters.
Oddly, the *initial* damage from SoB:W and SoB:WF does not seem to be affected by the TDR, but DoT from these skills and Burning Embers *is* increased by the TDR.
Tactical Offense Rating
Tactical Damage Rating is analogous to a melee or ranged weapon's DPS rating. A completely separate (but also new) concept is the Tactical Offense Rating (TOR). TOR is analogous to the new Melee Offense and Ranged Offense Ratings in SoM.
All three of these Offense Ratings are increased by stats.
Might -> Melee Offense Rating
Agility -> Ranged Offense Rating
Will -> Tactical Offense Rating
For LMs, each point of Will adds 10 points to your TOR.
In addition, gear and relics can add to your Tactical Offense Rating. The Adamant Gem of Dreams, for example, no longer says "+5% Tactical Damage," it says "+1200 Tactical Offense Rating".
At Level 65, 260 Tactical Offense Rating points are *roughly* equivalent to +1% Tactical Damage. There are diminishing returns, but they are not particularly painful.
Other bonuses to Tactical Damage stack with the bonus from your TOR in an additive fashion. For instance, the 3/5 bonus for MoNF adds 5% directly to this bonus (it is not a rating and therefore not subject to any cap). Your character panel shows your TOR and the overall percentage bonus to tactical damage.
The net tactical damage bonus T is a percentage multiplicative factor to the base skill damage B. I will call this Modified Base Skill Damage, M. Then
M = B * (1 + T) = (C * (TDR) + D) * (1 + T)
Skill Damage Bonuses and Tactical Direct Damage Legacy
Other bonuses may apply to specific skills or sets of skills. For instance, you may have a legacy that increases Burning Embers Initial Damage by X%, a Y% bonus to Fire Damage Skills from Flame of Anor, MoNF set bonuses and/or the Watcher set bonus, and a Z% bonus from the Tactical Direct Damage legacy. These bonuses generally do *not* appear anywhere on your character panel.
Each of these bonuses appears to stack additively, but separately from the tactical damage bonus.
The Final damage F which hits the target (and is subject to mitigation) in this case would be:
F = M * (1 + X + Y + Z)
F = B * (1 + T ) * (1 + X + Y + Z)
F = (C * (TDR) + D) * (1 + T) * (1 + X + Y + Z)
To summarize this final equation:
F: Final damage
TDR: Tactical Damage Rank of staff
C: TDR-dependent damage component of skill
D: TDR-independent damage component of skill
T: Tactical damage bonuses from MoNF, Tactical Offense Rating gear, and Will
X, Y, Z: Fire damage bonuses, skill-specific bonuses and Tactical Direct Damage legacy
I haven't studied in nearly as much detail, but I strongly suspect our healing skills work in a similar fashion, but of course they are affected by different ratings and bonuses.
In particular, it is worth noting that the amount of power transfered by Share the Power now depends on your Outgoing Healing Rating (and thus, your Will) and also on the Tactical Healing Rank legacy on your book. There is also a new staff legacy that gives a % bonus to Share the Power.
Will is therefore much more important now for a performant build, whether in a support role or DPSing.