It can change too.
They changed skills in IC (Racial passives).
They deleted the skillLine 2 in IC (Emperor) make the 3rd become the 2nd (Assistance moved from 3rd to the 2nd).
And they added a skillline in the 3rd position instead of the 4th with TG.
And for World it can change depending of skillline unlocking.
And for Tradeskills, skilllines are not even sames if you are starting game in EN , DE or FR.
And with a revamp, they can add skills too.
Plus, for 1 skill, you can have 12 abilityId. Per exemple here are abilityId of DK Skill 1 of Draconic Skillline (1st skill line).
Lua Code:
[SKILL_TYPE_CLASS] = {
["Draconic"] = {
[1] = {["skillPool"] = {
[0] = {[1] = {["id"] = 29012,},[2] = {["id"] = 33652,},[3] = {["id"] = 33655,},[4] = {["id"] = 33658,},},
[1] = {[1] = {["id"] = 32719,},[2] = {["id"] = 33662,},[3] = {["id"] = 33665,},[4] = {["id"] = 33668,},},
[2] = {[1] = {["id"] = 32715,},[2] = {["id"] = 33671,},[3] = {["id"] = 33675,},[4] = {["id"] = 33679,},},
},["at"] = ABILITY_TYPE_ULTIMATE,},
And with passive they can add unlimited #amount of passives ranks.
So yes, there is not real proper way to do it, you'll need to check at each new DLC.