Adjust Tornado damage.

It's still a no-brainer to use the alternatives, but a bit less so.  In a
typical late Zig scenario, damages of various spells are:

Refrigeration    600 in  10 aut
Tornado          700 in 100 aut
Shatter          700 in  10 aut
Firestorm (r=2)  650 in  10 aut, 1500 in 100 aut, 2550 in 230 aut
Firestorm (r=3) 1000 in  10 aut, 2700 in 100 aut, 3800 in 240 aut
(chance for a big Firestorm is 25% at pow 100, 50% at pow 150)

After testing a number of scenarios, this one seems to be roughly average.
It had a bunch of Pan lords plus two turns worth of spawns, nearest one
touching the player.  Furniture was: none at radius 1, two squares at radius
2, one at 3, one at 4, seven at 5 (ie, below 10%).  Most non-Zig scenarios
have plenty of walls.  Shatter was strongly biased against: 2/3 Pan lords
can fly, so do nearly all spawns (eyes, neqoxecs, balrugs, fiends) -- in
this set only a hell beast and two green deaths were on foot among minions.
Most lords have rC and rF, spawns rarely.

The contender with a direct comparison, Shatter, was strictly better: 10
times better damage per second, same mana efficiency.  After the adjustment,
5 times better dps but half the damage per mana makes Shatter still a better
choice but at least not strictly.

Firestorm is strictly better for this set even after doubling: you can
either let them simmer for better total damage, or burn extra mana for rapid
fire.

1 files changed, 1 insertions, 1 deletions

diff --git a/crawl-ref/source/spl-tornado.cc b/crawl-ref/source/spl-tornado.cc
index ea710da28b..825b8081d4 100644
--- a/crawl-ref/source/spl-tornado.cc
+++ b/crawl-ref/source/spl-tornado.cc
@@ -323,7 +323,7 @@ void tornado_damage(actor *caster, int dur)
                             float_player(false);
                     }
                     int dmg = apply_chunked_AC(
-                                div_rand_round(roll_dice(6, rpow), 15),
+                                div_rand_round(roll_dice(12, rpow), 15),
                                 victim->armour_class());
                     if (dur < 0)
                         dmg = 0;