The Current RAW Half dragon template reads:
Creating a Half-Dragon
“Half-dragon” is an inherited or acquired template that can be added to any living, corporeal creature (referred to hereafter as the base creature). A half-dragon retains all the base creature’s statistics and special abilities except as noted here.
CR: Same as the base creature + 2 (minimum 3).
Type: Creature type changes to dragon. Do not recalculate hit dice, base attack bonus, or saving throws.
Armor Class: Natural armor bonus improves by +4.
Special Qualities and Defenses: A half-dragon gains darkvision 60 feet; low-light vision; and immunity to sleep, paralysis, and energy of the same type as its breath weapon.
Speed: A half-dragon has wings. Unless the base creature has a better fly speed, the half-dragon can fly at twice the creature’s base land speed (average maneuverability).
Melee: A half-dragon has two claw attacks and a bite attack. If the base creature can use manufactured weapons, the half-dragon can as well. A new claw or bite attack deals damage as appropriate for the half-dragon’s size (see “Natural Attacks”).
Special Abilities: A half-dragon retains all the special attacks of the base creature and gains a breath weapon usable once per day based on the dragon variety (see below). The breath weapon deals 1d6 hit points of damage per racial HD possessed by the half-dragon (Reflex half; DC 10 + 1/2 creature’s racial HD + creature’s Con modifier).
Dragon Variety Breath Weapon
Black or copper dragon 60-foot line of acid
Brass dragon 60-foot line of fire
Blue or bronze dragon 60-foot line of electricity
Gold or red dragon 30-foot cone of fire
Green dragon 30-foot cone of acid
Silver or white dragon 30-foot cone of cold
Abilities: Increase from the base creature as follows: Str +8, Con +6, Int +2, Cha +2.
Skills: A half-dragon with racial Hit Dice has skill points per racial Hit Die equal to 6 + its Intelligence modifier. Racial class skills are unchanged from the base creature’s.
However for my game I’m planning mega dragon wars arch and one alchemist on the hero side did an experiment with dragon’s blood resulting in modified half dragons:
Creating an alternative Half-Dragon.
CR: Same as the base creature + 2 (minimum 3).
Type: Creature type changes to dragon. Do not recalculate hit dice, base attack bonus, or saving throws.
Armor Class: Natural armor bonus improves by +4.
Special Qualities and Defenses: A half-dragon gains darkvision 60 feet; low-light vision; and immunity to sleep, paralysis, and energy of the same type as its breath weapon.
Speed: A half-dragon does not have wings. Instead of fligh; the half-dragon gained increased ground speed of 40 ft from the base race.
Melee: Gains no natural attacks.
Special Abilities: A half dragon instead of gaining a breath weapon gains bonus feats.
Abilities: Increase from the base creature as follows: Str +8, Dex +4,Con +6.
Bonus Feats: Endurance, Diehard, Great Fortitude, Lightning Reflexes
Skills: A half-dragon with racial Hit Dice has skill points per racial Hit Die equal to 6 + its Intelligence modifier. Racial class skills are unchanged from the base creature’s.
Physical appearance: Same as base race; 25 % of mutation (scales for skin, dragon shaped head, etc)
With the changes I made would you still consider it a +2
The immunity was meant from the dragon type.
I would argue they are never used, at early use “bite/claw/claw” does a lot more damage then one melee swing. It’s only at mid to late late levels do the natural attacks become obsolete.
The drop in mental stats was was more of it didn’t make sense for a “dragon super soldier” to gain mental stats.
I gave it 4 feats. But I looked at other +2 templates and some that gave a lot more powerful abilities gave 4 feats. Example Deathknights.
How about just giving them fighter levels, with then using the variant multiclassing rules with the Sorcerer? Pick the Draconic Bloodline AND the Linnorm Wildblood option (to replace claws with elemental spit).
Yeah, of all the variant rules, variant multiclassing seems to be the least "outlandish" of the bunch. You trade regular feats with dialed-down class features, as part of a "part-time class".
overall I don't see much issue except the +40 movement is over the top, and trading +2 in 2 mental stats for +4 for 1 physical stat is unbalanced. I would say change the movement to +10 over normal movement t(so humans get 40') and make it +2 to DEX and it's probably ok overall.