Cons vs Deacon:

Explosive Resist Hole: Warrior Drones and autocannons are the Thalia’s worst enemy.
An active Enduring Explosive Armor Hardener is required on every Thalia. 
Signature bonus negated by Skirmish boosts.
A Deacon with Skirmish boosts has a 28.3 sig radius, a Thalia has 23.8
This means the deacon’s +7.5% to armor hit points (which is cumulative) outshines the Thalia’s sig bonus whenever there are skirmish boosts. There will almost always be skirmish and armor boosts from pontifex/magus in any fleet with either thalias or deacons. 
The Thalia has the same drone stats as a the Deacon, whereas the Oni and Exeq have a flight of medium armor in lieu of the Aug/Guard light armor drones.
Now let’s use a sane and cheap fit for both of them. I don’t care how either outperforms the other with super blingy tournament fits (and frankly neither does anyone else).
For both (therefore getting the same repping power and cap use bonus).
Highs: Iax Enduring Remote Armor Rep x3.
Rigs: Small remote repair aug (tech one) x2.
Deacon Cap Stable:
Deacon Lows:
400mm tech II plates.
DCU II
Reactive Armor Hardener
Multispec Energized II
Cap power relay II
Deacon Mid:
1 MN Enduring AB
Enduring Ewar mod or Sebo or web/scram (your choice)
Thalia Cap Stable:
Small cap bat II
1 MN Compact (a downgrade from enduring)
Any Tech II EWAR mod or tech II sebo or web/scram (your choice).
Lows:
400mm compact (a downgrade from tech II plates)
Cap power relay II
Enduring Explosive Armor Hardener
Reactive Armor Hardener (no damage control, you need a reactive vs RLM’s and autocannons!)
Thalia Variant
Mids:
Small compact pacid bat.
1MN Enduring
Any named EWAR/sebo of your choice.
Lows:
400mm compact
Multi spec Energized II
Damage Control II
Coreli AAtype Explosive Coating (these are always cheap, less than 250,000 ISK.
EHP: Deacon, Thalia, Thalia Variant: 16,800 vs 9,190 vs 10,800
Speed and agility (measured by align time):
Deacon: 1058m/s and 6.56s
Thalias : 1126m/s and 6.37s
Thus, the extra mid slot of thalia is forced to be a cap battery, while both the Deacon and Thalia can fit an EWAR mod or sebo.
The only advantage the Thalia has is it can bring a single tech 2 ewar mod over a named, whereas the Deacon has twice the EHP.
For swift moving wolf packs, where cap stability isn’t even considered, the Deacon be dual propped (while still having significantly more EHP than the Thalia!) and the Thalia will have zero tank is they dual prop.
Given the above, I propose the following buffs:
Give the Thalia a n% capacitor size bonus per level. We’ll start with n = 12.5% for this thread.
Allow the Thalia to have 5 light drones deployed and a drone bay that can hold a total of 15 drones for combat, ewar or repping. This would be +5 drone bandwith per level.
Like the Exeq and Oni, they should also get +100% to logi drone transfer
Move one High Slot to Medium and reduce the logi cap bonus from 10% per level to 3% per level. If the Thalia pilot wants the same repping power as the Deacon, then he needs to deploy and manage his logi drones.
At the same time, removing the third high slot fixes the powergrid issues.
Give a minor bonus to all EWAR modules (one half the bonuses given to any EWAR platform).
This allows the Thalia to bring two partially bonused Ewar mods and pack of light drones (that need not be logi drones) at expense of half the EHP of the Deacon.