The 2-star crafted tanking set is too cheap to craft compared to other sets. The tank set has two items that count as two pieces of gear; the Heavy Darksteel Armor counts as both Helm and Chest slots and the Heavy Darksteel Flanchard counts as both Legs and Feet slots. Both of these items only require one Darksteel Ingot to make, which needs 9 Coke, one the 125 Tomestone of Philosophy materials.

Meanwhile, there are pieces in other sets that require 18 Tomestone materials to make just one piece (Darksteel Mitt Gauntlets and Gryphonskin Kecks just to name two) in addition to still needing more Tomestone materials because other sets don't get the two-for-one item deals the tank set does. So even if the Heavy Darksteel pieces I mentioned were changed to require 18 Tomestone materials each the tank set would still be cheaper to make than other sets.

To really even things out both two-for-one items should require 18 Tomestone materials to make since they cover two slots of gear and one of the tanking set items should require an additional 9 Tomestone materials since every other set has an item that requires 9 extra to make just one piece.