For my case usage the guardian buffs up my minions he is not really there to even guard. I could get a jewel with minions have % chance to taunt that fits into sockets in my passive skill tree. Some point I will when I find the right one since I have quite a few minions.

Most people later in the game tend to go with a golem of some sort that helps buff them in some way. You tend to have stuff like stone, lighting , flame, ice or chaos golem.

Using a Vaal Orb is very tricky, more times than not it will do nothing or “brick” (make worse) the item you used it on. Once an item is corrupted you can’t do anything else to it. It might be better off selling them to another player (unless you are playing solo self-found incursion league) and buying upgrades.

One Vaal Orb is around 1.9 Chaos. So if you get a couple more you could just click on “contact and copy/paste the message in game to find a buyer for them and meet that person up in there hide out. There is one buyer at this time trying to buy 5 Vaal Orbs and he will pay you 9 Chaos Orbs.
http://www.pathofexile.com/trade/exchange/Incursion/EB9LC5

Otherwise you can just save the Vaal’s for when you are maping. Once you get to red maps you need to Vaal each rare one to get the bonus objective. On top of that there a slight chance of getting +1 level on that map. I’ve only had it I think happen once so far for a map to get an extra level after being vaal.