I completely agree with the skill point spend on Inferno. Immolate, Flashpoint, Pyromancer and Fire Mine are arguably the most valuable 4 skill points you will spend for the entire game as a mage, including as a low level one.
I also agree with taking Barrier at low level. I'll say more about this in a second.
My preferred low level build diverges from StarFlorge's at this point, which I'll describe in more detail below.
If you are running solo, stop reading here. StarFlorge's build is great for a solo mage and that's all you'll need. Also, even if you aren't running solo but you insist on controlling your IQ as the only mage in the party, you might as well stop reading here as well.
I'll start with a tip of my own: for 8 skill points and lower, optimize the build of your entire party, rather than a single character in isolation. Since you have so few skill points individually, it makes sense to treat the party as a single pool of abilities, shared out across the four party members. That means intentionally leaving gaps in the abilities of one character, because another character can cover that area better. You should also think about which character you should actively control, and more importantly, which characters the AI is better at controlling. Yes, there are some things the AI can do better than you!
Unless this is your first playthrough, you know what you are up against as a low level mage. There are a fixed set of set-piece quests and boss battles to deal with: Champions of the Just (Envy demon) or In Hushed Whispers (Alexius), and In Your Heart Shall Burn (Haven raid, Knight-Captain or Fiona). Since you know what to expect, you can optimize your party's abilities accordingly.
For example, I find it useful to dedicate one mage in the party to spamming Barrier, and I let the AI control that character, because it's great at putting Barrier on the character that needs it. That means (obviously) taking Barrier, but also Elegant Defense. Lower cooldown means more Barriers cast per minute.
Because I want that mage to spam Barrier, I don't want him to use other abilities that use a lot of mana. That rules out Energy Barrage (50 mana). While I completely agree with the reasons given for taking EB and I do usually give at least one mage EB, the mana cost needs to be considered in the overall design of the party.
Even Fire Mine is debatable at 35 mana. At a minimum, if my Barrier spammer is also my Inferno mage, I disable Immolate in that character's AI to make sure that his mana isn't split three ways between Barrier, Immolate and Fire Mine.
Another reason not to give EB to the Barrier spammer is because that skill point might better be spent on Clean Burn. Every cast of Barrier or Fire Mine will help reduce cooldowns for the next cast of Barrier or Fire Mine, with Clean Burn enabled.
I prefer to take the Wildfire or Consuming Fire upgrade to Immolate over Fade Step. Fade Step, or rather, Frost Step is very useful, but I usually have something I want more in the build.
Finally, for my Barrier spammer, I do take Guardian Spirit to help with survivability. The longer he is alive, the longer the rest of the party stays alive.
If I have two mages, I might not have Barrier, or any Spirit points, on the second one. I might use those points on more damage dealing skills or passives. For example, if I've given EB to a battle mage, I usually also give them Conductive Current to buff their damage. On the other hand, I might spend 3 points in Spirit to get Dispel, particularly for the Haven raid against Venatori and their annoying fire mines.
So that you have something concrete to look at, here is an 8 point build for a Barrier spammer, with a side of Fire Mine for damage. I'd let the AI control this character during the boss battle. The abilities are in priority order, so if you only have 7 points, drop the last skill, and if you only have 6 points, drop the last two, etc.
Barrier, Elegant Defense, Immolate (disabled), Flashpoint, Pyromancer, Fire Mine, Guardian Spirit, Clean Burn