Silversea
Savannah Queen
There is absolutely no way a level 50 Galvantula can take less than half damage from a level 100 Emboar. With the level difference, Galvantula would go down...no ifs, ands, or buts.
Did you both have your Pokemon set to level 50? If both were at level 50, a Timid (-Att +Spe) Emboar with 0 IVs and 0 EVs in attack would still do more than half.
Emboar - Timid - Level 50 - 0 IVs & 0 EVs in Attack
Galvantula - Impish - Level 50 - 31 IVs & 252 EVs in Defense & HP
Flare Blitz (120 base power) takes away somewhere between 72%-86%. I highly doubt you invested those EVs into an Impish Galvantula because that isn't focusing on its best stats. If Emboar was an in-game Emboar, there would be some Attack EVs there as well. Even still, if this WAS the case, Flare Blitz still took well over half.
Are you sure your Galvantula wasn't level 100 and his Emboar was level 50? If so, then Galvantula's strength can't be based off of it since that wasn't a fair fight.
Anyway, to answer the main question in this thread, no I don't think Electric-types are OP. They're pretty weak defensively and a lot of the pure Electric-types suffer from shallow movepools.
What if you took reflect into question? Water sport? Rain dance?