I just crunched some numbers on warscrolls that changed between 2.0 and 3.0 (in cost or abilities/stats). This excludes support heroes as their abilities are hard to quantify. Note that this is damage in combat only and defensive abilities only look at wound per cost change (as the saves are basically the same across the board)
Efficiency is total point cost divided by total damage output in 1 combat phase based wholly on their warscroll. Lower is better, differential was calculated comparing old vs new efficiency. This does not include ranged damage... so expect a minor increase in efficiency (maybe 1-3% increase) across the board due to throwing axe buff for new 3.0 warscrolls.
Runeson Magma
26% increase Offensive pt efficiency
14% decrease Defensive pt efficiency
12% net increase in efficiency
Runefather Magma
15% increase pt efficiency in combat output (31% for 1 turn when using +1 atk ability)
10% decrease in pt efficiency in defensive ability
5% net increase in effiency (21% for 1 turn)
Runefather foot
6% increase O efficiency (31% for 1 turn)
20% decrease in D efficiency
-14% net efficency (+11% for 1 turn)
Runeson foot
65% increase in O efficiency
Same D efficency
+65% net efficency
HGBZ
16% reduce in O efficiency
16% reduce in D efficiency
16% reduction in total pt efficency (do note that it is MUCH easier to keep runseon/father on foot alive to keep ward going, but harder due to wholy within so I call that a wash)
Vulkite axe
30% reduce in O efficency (4% increase on charge)
6% reduction in D efficiency
36% reduction in total
Vulkite Shield
48% reduction in O efficiency
10% increase in D efficiency
58% reduction in total efficiency
Auric Hearthguard
5-10% increase in efficiency against armored targets (close combat only). Minor range debuff has utility that I couldn't figure out how to calculate.
50% decrease in efficiency against monsters
Hard to calculate how much reduction, but given their role was pretty much ONLY to kill monsters lets say they've reduced in efficiency by 40% (maybe 30% if you see any value in movement debuff)
Based on the above, we can see a huge trend reducing defensive efficiency and increasing offensive efficiency for almost all FS heroes. We also see nerfs in overall efficiency across the board for non-hero FS warscrolls. The unit hit least hard by this was hearthguard berzerkers - which are still our most points efficient unit by far both offensively and defensively assuming you keep a hero in range.
Keep this with a big grain of salt as this is JUST warscrolls. Allegiance abilities overall are better in my mind, ur-gold is definitely better and lofnir is better for sure. Hermdar was almost certainly a bit better for HGBZ heavy builds. in 2.0 however. Magic items are better across the board. Support abilities from heroes are better offensively and worse defensively.
For example, factoring in Lofnir the defensive efficiency of magmas becomes the same instead of a reduction from 2.0 to 3.0. Factoring in Vostarg and offensive efficiency on the charge of vulkites with axes becomes 39% better than vulkites on the charge in 2.0.
If you add in additional offensive capabilities not present in 2.0, such as +1 attack from runefather or the +1 damage from flamekeeper, magic item combos we are looking at damage potential that simply was not possible in 2.0 tome.
Defensively the army took a significant hit, in particular against regular damage. However, there is now a plethora of ways to get a 5+ or 6+ wardsave... plus an amazing way to keep foot sons and foot fathers alive. Overall I'd say our defensive ability against mortal wounds went up and all other damage went down. Battlesmith is a great defensive hero and flamekeeper great offensive hero if you can keep them alive (which you won't be able to against 90% of competitive lists).
Haven't played any games yet, but I think the 3.0 tome encourages a bit more variety in gameplay styles. From what I can see we have an ultra aggressive charge list (vostarg), defensive focused list (HGBZ and foot heroes, Greyfyrd), monster list (lofnir), or combined arms list (grefyrd or vostarg). In 2.0 I don't think we had an aggressive charge list so that is a new playstyle overall that we didn't really have before - I could see a 70 vulkite axe list backed up by several flamekeepers being worth testing out.