I believe that Regulus has much in common with the dwarf sniper and luna in WC3 DoTA maps. He seems overpowered when played by someone who heavily uses atk move (alt + click) and is skilled at using mines to defeat large numbers of minions. I often find that in multiplayer games when playing Regulus, I can out level most other characters (usually at level 13-14 when others at 7-9) and often outdamage them by 3-5x by the end of the game using cheap items, and well placed sniper shots and mines to get many hero kills when they are running. If you add a haste item (favor item usually) or a critical hit item, he becomes a powerhouse that is hard to stand up to early in the game, without ganging up.... and IMPOSSIBLE to stand up to later on. I hesitate to call this a balance issue yet as I've only been playing a few days and haven't had the chance to evaluate the other characters and their abilities, beyond Rook, who can also be equipped and skills built out to kill most characters in 1-4 hits. Perhaps this will change as more human players are placed in Pantheon games.
In light of this, his (Regulus') ability to hit towers from out of their range after the 2nd point of range increase skill, does make it considerably easier for forces of light to get a jump on killing defenses early on. Games with multiple people playing Regulus have a distinct advantage in this regard in the early stages of the game, and if 2 people playing Regulus are skilled with snipe and good at watching for weak heroes to kill from afar, it does not take long to chain kill your enemies early on (which impacts their gold income heavily), then kill their towers without getting hit, and often guarantees a win with very little effort.
In the later stages, there is no way three level 7-9 characters can stand up to a Regulus with a giant belt (100% chance of cleave which works with ARROWS!!!!!!? This seems like a bug, as he can decimate huge numbers of minions in just a few shots, and again, coupled with land mines he can kill anyone usually before they are in melee range at level 10+).
Yet, having played a few of the other characters, it seems that similar scenarios are available with most, using the right combination of items and skills. Namely Rook and his aoe damage hammer slam that is like 1600 dmg after 2 pts.
I will reserve judgement on these balance issues for the time being, but these are my initial observations.
P.S.
I strongly disagree with raising other heroes range to match his. There are far more creative ways to counter a single character's ability/skills than giving another character the exact same talent. Traps, teleports, etc are all present in the game and negate long range if used properly/intelligently and above all - the way to kill a character that can attack from farther away than you or do more damage than you, or is just killing more of your team than is healthy is good teamwork, and cunning. Develop strategies/tricks with each character you play to counteract such things, and use them often. 
