According to last month's stats, those three add up to ~15% of OU. They were also oppressed by the now-Uber Genesect, which means that they could be seeing more usage this month. And here's the kicker: Scarf Salamence. We are now up to 25% of OU, and you are not getting past that shit with a +Att nature.
Having done the calcs just now between Heatran and Ferro, the damage boost vs bulky Steels is a 4-6% increase at best (EX: +1 LO Outrage vs 252 HP Heatran w/Jolly: 48.2% - 56.7%; w/Adamant 52.8% - 62.4%), so you're probably not going to notice that in an actual match. However, you will notice getting bitchslapped by Jolly Luke or Timid Hydreigon all of the sudden, Pokemon that Salamence is usually called upon to check. Covering contingencies is always better than greed.
(02:53:55) +shrang: sleep is epic
(16:14) .No Scrafty in UU.: CBtar?
(16:14) .No Scrafty in UU.: that sounds like a not bad set
(16:04:25) +Steamroll: nobody likes me
@Relados: snowflakes has no sense of humor